I.Application Infrared camera lens with spectral range 0.8 ~ 2.4 u m. II. Requirements Applicable wavelength: 3 ~ 5 μ m EFL: 1.0 in (25 mm) Lens quantity: no more than three pieces Lens maximum diameter: less than 15 mm Lens facial type: all spherical Lens material: optical glass Lens gross weight: less than 10 g Detector size: 1 in (16 mm) Maximum aperture: 2 Rear intercept: more than 16 mm Resolution: more than 20 lp/mm@0.5; 24 lp/mm@0.4; 36 lp/mm@0.3 III. Features This lens belong to middle infrared lens which needs expensive but rare material and low transmittance, so lens thickness shall be as thin as possible. Due to long wavelength, and requirements on resolution is low. This design type is similar to Cooke triplet. IV. Result