Optical measurement system for infrared spectral region to observe and measure geometrical characteristics of object in proximity of observing system, has negative lens whose material has high dispersion than that of positive lens

摘要

The system (1) has a lens (6) arranged between an object-side lens (3) and an image-side lens (4). The lenses (3, 4) are formed as positive lenses and the lens (6) is formed as a negative lens with an aspheric outer surface. Material of the lens (6) has a high dispersion with respect to material of the lens (3). The material of the lens (6) has a smaller refractive index with respect to the material of the lens (3). The lenses (3, 4) are made of silicon and the lens (6) is made of calcium fluoride. The lenses are convex-concave lens in an imaging direction.