Application of diffractive/refractive hybrid lens for night-vision relay lens system

Night-vision relay lens system with a diffractive/refractive hybrid lens which relays the image between the phosphor image plane of an image intensifying (I.I.) tube and a 35mm film single-lens reflex (SLR) camera was designed and made. The optical system consists of 5 lenses including 1 diffractive/refractive hybrid lens, whereas the conventional all refractive lens system has 7 lenses. After design and manufacture we compared the optical performances of both two lens systems. Since diffractive/refractive hybrid lens has an excellent feature to correct chromatic aberrations in the broad bandwidth visible spectral region, we could obtain the much higher resolution and better image quality from the lens system with the hybrid lens than those from the conventional lens system. The diffractive surface was fabricated with photolithographic methods to get 8 leveled zone structure and its micro profiles were inspected with scanning electron microscope (SEM) and atomic force microscope (AFM).