Patent ID: 8049884

Claim:
A spectrophotometer for measuring a transmission characteristic of a liquid sample, including: an optical system for vertically forming a tramsmission path of a measurement light in an open space; and a sample holding unit, which is inserted in the transmission path of a measurement light formed by the optical system, for holding a liquid sample, wherein the sample holding unit comprises: a) a sample stage which is composed of a base material and a light-transmitting body projected with respect to the base material and an upper surface and a lower surface of the light-transmitting body are both horizontal; and b) a window plate which is made of a light-transmitting material and can be held above the sample stage and on the liquid sample dropped onto the upper surface of the light-transmitting body, in such a manner that a boundary phase parallel to the upper surface is formed at a predetermined distance from the upper surface, and thereby allows a measurement to be performed by: bringing the lower surface of the window plate and the upper surface of the light-transmitting body closer to each other to reach the predetermined distance after the liquid sample is dropped onto the upper surface of the light-transmitting body; and with the liquid sample touching the upper surface of the light-transmitting body and the lower surface of the window plate, delivering a measurement light from above or below the liquid sample and measuring a light which has passed through the liquid sample downwards or upwards.