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New generation optics for NVIS
Currently, analog NVIS night vision systems technology is very mature, so the new III Generation image intensifier tubes have a very high resolution, usually around 74pl/mm. However, the optical systems integrated in the system usually have a lower resolution, so the final resolution of the whole system is limited by the optics and not by the tube itself.
New optics for high-end night vision systems
Working always for excellence, and within the framework of COINCIDENTE program (Ministry of Defense of Spain), ASE Optics developed a monocular with 1x magnification, with the aim of producing high-end night vision binoculars and goggles.
To reach the objective, we designed both optical subsystems (objective lens and eyepiece) using lenses that include aspheric surfaces based on the standardized polynomial QBFs to improve not only the resolution and transmission of each subsystem, but also the distortion of the ensemble. In addition, during the optimization, a balance between weight, dimensions and optical quality was made, considering all the time both, productivity and functional criteria.
Figure 1. Objective lens drawing and design
In the Figure 2 (below) the image simulation of the scene through the objective lens is shown. We can notice how the illumination and distortion decreases in the extreme field, but at the same time we can also notice how the image inside the reticle is clearer.
In the specific case of the eyepiece, ASE Optics made a design for a wide eye relief; 25mm considering the movement of the eyeball, for a better adjustment of the aspheric QBF surface introduced. In the next figure, we show the optical design of the eyepiece with the simulation of the eye pupil.
Results: more resoltution, more and better transmission
Both subsystems reach resolutions higher than the 80 cl/mm in the focal plane and with transmission better than 93%. Since they are designed to fit together, their distortion is compensated: the distortion of the monocular is less than 4% for a total field of view of 40º. Also, it is important to remark that the weight of these subsystems is reduced, a 15% less compared to other commercial systems: better ergonomics, better user-experience.
Authors: Marta de la Fuente, CTO in ASE Optics
Andrés Cifuentes, CEO of ASE Optics