Patent ID: 7864438
Filing Date: 2011-01-04
Classification: G02B

Abstract:
1. An image forming lens for receiving parallel beams of light emitted from an observation target object and emerging from an infinity-designed objective lens of a microscope and forming an image of the observation target object in a predetermined position, comprising in order from an object side: a first lens group having positive refractive power; and a second lens group having negative refractive power, said first lens group comprising a positive lens and a negative lens, wherein when nd denotes a refractive index of glass materials of the lenses which constitute the first lens group and the second lens group with respect to d-line, nh denotes the refractive index of the glass materials with respect to h-line and nt denotes the refractive index of the glass materials with respect to t-line, and νdht and a partial dispersion ratio Pht are defined by the following conditional expressions; the following conditional expressions are satisfied: where νdht 1 and Pht 1 respectively denote νdht and the partial dispersion ratio Pht of the glass material of said positive lens configuring said first lens group, and νdht 2 and Pht 2 respectively denote νdht and the partial dispersion ratio Pht of the glass material of said negative lens configuring said first lens group, a transmittance of each of the glass materials of all said lenses configuring said first lens group and said second lens group with respect to the light having a wavelength of 340 nm is equal to or larger than 50% per glass thickness of 10 mm, and the transmittance of each of the glass materials of all said lenses configuring said first lens group and said second lens group with respect to the light having the wavelength of 360 nm is equal to or larger than 80% per glass thickness of 10 mm.