Optics Assemblies available from Stock
By leveraging our broad portfolio of optical lenses, our supplier has been implementing sophisticated integrated optics assemblies available from stock that include precision-molded lenses using high-quality chalcogenide glass, assembled into solid and threaded units and featuring passive athermalization for -40°C to +85°C as well as high-volume and cost-effective manufacturing.
Our thermal imaging optics assemblies range from models with a very wide horizontal field of view (FoV) of 120° and 1.5 mm focal length to those with a narrow FoV of 12° and corresponding focal length of 50 mm. While assemblies with focal lengths from 1.5 to 9 mm contain single lenses, the assemblies with focal lengths from 15 mm to 50 mm are doublets. Threads ranging from M12 to M34 allow for mounting the assemblies to detector units or cameras.
For each of the optics assemblies an optimum detector format is recommended, ranging from 80 x 80 / 34 µm detectors all the way to 640 x 512 / 10 µm detectors. Together with our supplier, we can design custom assemblies, including complex imaging systems for camera systems, to your exact specifications. Please get in touch with the AMS Technologies infrared imaging experts to discuss a customized solution for your requirements. Additional services include thermal analysis and athermalization for better performance across a large temperature range.
Our optics assemblies can be combined with our range of discrete detectors and arrays based on InGaAs, PbS, PbSe, Si and other detector materials. We also provide ready-to use cameras for the visible and infrared wavelength ranges as well as dedicated x-ray cameras.
Additionally, a wide range of optical lenses is available as well as other optics components like optical windows, optical filters, optical mirrors, optical prisms, etalons or optical beamsplitters. Our portfolio of optomechanics and motion control includes optical tables, breadboards, platforms and posts, but also optical mounts, rotation, linear and tilt stages or motion controllers.
Long wave infrared imaging assemblies are used in thermal imaging to detect energy in the infrared spectrum, so long wave thermal imaging optical assemblies include lenses that are transparent in the long wave infrared (IR) range.
How to Choose the Right Thermal Imaging Assembly
Before starting any calculation or selection, you need to know the application’s constraints: What is the target (person, vehicle, building, etc.) and its dimensions? What will be the estimated observation distance? What is the configuration of the camera (QVGA, VGA, HD, etc.)? Is the camera fixed or portable?
Thermal imaging is often classified referring to “DRI” (Detection, Recognition, Identification). There are a lot of complex models and calculations available in the industry to determine DRI for optics assemblies. The Johnson model, one of the simplest methods for DRI calculation, has been around for decades. It uses four basic parameters, two defined by the system – the focal length of the lens and the pixel size of the detector – and two defined by the application – the object size or height and the number of pixels that you want your object to cover.
The object height is set by the “critical dimension”, typically 0.75 to 1.5 m for humans as targets of security and surveillance applications. The required image height is set by the detector pixel size times the minimum number of “pixels on target” for DRI:
- Detection: 1.5 pixels on target (POT)
- Recognition: 6 pixels on target (POT)
- Identification: 12 pixels on target (POT)
These values are an absolute minimum, for many applications a higher number of pixels on target is required.
The maximum range for DRI can then be calculated based on the information above and the effective focal length of the lens, with the formula:
Range = (EFL * Critical Dimension) / (POT * Pixel Size)
This formula can be re-arranged to solve for e.g. providing the focal length based on a given range. Pay attention to the units of each value as they usually differ a lot (e.g. pixel size = µm, critical dimension = m, EFL = mm). An example: Assuming you want to aim a lens with an EFL of 75 mm in front of a detector with 17 µm pixel size on a target with a size of 1.5 m. Applied on this situation, the formula gives a detection range of (75 mm * 1.5 m) / (1.5 POT * 0.017 mm) = 4412 m, a recognition range of (75 mm * 1.5 m) / (6 POT * 0.017 mm) = 1103 m and an identification range of (75 mm * 1.5 m) / (12 POT * 0.017 mm) = 551 m.
If you can’t determine a standard optics assembly matching your requirements, we are happy to assist you. We have many years of experience in the development and design of customized assemblies in cooperation with our suppliers. Contact us now to arrange an appointment.
Alternative Terms: Objective; Optical Lens Assembly; Lens; Thermal Imaging Assembly; LWIR Imaging Assembly; Infrared Imaging Assembly