The utility model relates to an
optical imaging system, in particular to a
visible infrared dual-band
refraction and reflection optical
system based on a free-form surface shared beam shrinking lens. The technical problem that an existing total reflection type
earth remote sensing system and a
refraction and reflection type
earth remote sensing optical system are difficult to meet the overall requirements of compactness,
stray light, convenient adjustment and large view field is solved. The system comprises a beam shrinking unit, a dichroic mirror, a visible TDI
imaging lens group, a reflecting mirror, an
infrared TDI
imaging lens group, a visible switching reflecting mirror and a visible area array
imaging lens group, wherein the beam shrinking unit and the dichroic mirror are sequentially arranged along a light path; the visible TDI imaging lens group, the reflecting mirror and the
infrared TDI imaging lens group are arranged on a reflecting light path of the dichroic mirror; the visible area array imaging lens group is arranged on a reflecting light path of the visible switching reflecting mirror; the beam shrinking unit comprises a
primary mirror, a
secondary mirror, an axis folding mirror and a third mirror which are sequentially arranged along a light path; the
primary mirror and the
secondary mirror are coaxially arranged; the included angle between the normal of the folding-axis mirror and the
optical axis of the system is greater than 45 degrees; the third mirror is a free-form surface reflecting mirror, and emergent central view field light of the third mirror is perpendicular to primary and
secondary mirror axes; and the dichroic mirror is arranged on an emergent light path of the third mirror.