SPECTROPHOTOMETER

PURPOSE:To quickly change the size of luminous flux in accordance with the size of a sample to be measured and the contents of measurement by arranging a plurality of different masks capable of changeover at the position near to the image-formation point of the mask of a light source and fitting a graduation wherein the measuring conditions are clearly stated to a sliding mechanism of transferring a condenser lens. CONSTITUTION:White light emitted from a light source is separated into sample light B5 and object light BR by a spectroscope. The image of the mask of the light source is formed on a mask provided to a mask changeover part 4 by a toroidal mirror. The mask is formed into two-step changeover. A first step is formed into a fixed mask. A second step is formed so that the mask fitted to a shaft is overlapped on the fixed mask of the first step by rotating a handle 28 at 90 deg.. The image-formation point (the vicinity of a sample 11) of the image of this mask can be arbitrarily controlled by the toroidal mirror 3d and a condenser lens 7 in a sliding mechanism part 9 wherein a pointer is allowed to coincide with a graduation 8 previously decided by calculation.