Patent ID: 7598483

Claim:
An optical element comprising: a light-emitting prism including a light-output face from which a light to be emitted to a sample is outputted; a light-receiving prism including a light-receiving face which receives the light returned from said sample; and a light intensity-reducing part provided between said light-emitting prism and said light-receiving prism; wherein said light intensity-reducing part is a light-blocking part provided between said light-emitting prism and said light-receiving prism; said light-emitting prism and said light-receiving prism are combined to form a recessed part with which said sample makes contact; and a light outputted from said light-output face enters said light-receiving face by traveling straight in said sample in contact with said recessed part, wherein said light-output face of said light-emitting prism is a first slope part which is planar and in contact with said sample; said light-receiving face of said light-receiving prism is a second slope part which is planar and in contact with said sample; and said first slope part and said second slope part are facing to form said recessed part, and a cross section of said recessed part in the direction vertical to said first slope part and said second slope part is roughly a shape of the letter V, and said optical element further comprising a spacer provided between said light-emitting prism and said light-receiving prism.