A catadioptric optical system includes, in order from an object side to an image side and arranged along an optical axis, a first catadioptric unit, a second catadioptric unit disposed in axial alignment with the first catadioptric unit and with a space therebetween; and a lens group disposed in axial alignment with the first and second catadioptric optical units. Light rays arriving from an object plane undergo a first reflection at the image-side surface of the first catadioptric optical unit, a second reflection at the object-side surface of the first catadioptric optical unit, a third reflection at the image-side surface of the second catadioptric optical unit, and a fourth reflection at the object-side surface of the second catadioptric optical unit. Advantageously, the sum the outward Petzval curvatures is cancelled out by the sum of inward Petzval curvatures.