Abstract: A CT computed tomograph comprises a scanner (51) which surrounds a living body of a person to be examined. Ultrashort light pulses of the ith wavelength are applied to the living body from a sample light transmitting path (80k) corresponding to the kth cell of this scanner and the sample light pulses received by a sample light receiving path (81l) corresponding to the lth cell and reference light pulses transmitted from a reference light path (79) and a delay light path (78) are converged by a converging lens (75). A CPU(64) counts photons outputted from a photomultiplier (22) based on the converged light pulses and calculates an average value by averaging a predetermined number of count values. A delay amount of the reference light pulses through the delay light path (78) is changed based on the average value and, based on delay time and an average value in the delay time, a photon count value S.sub.

Abstract: In a tissue metabolism measuring apparatus, light sources (31 to 33) emit rays of different wavelengths; the rays are branched as reference light pulses and sample light pulses through optical fibers (38 and 39); the sample light pulses are transmitted through a living body to be examined; the reference light pulses are delayed by means of mirrors (48 to 50); the sample light pulses transmitted through the living body and the delayed reference light pulses are collected by a lens (44); based on the collected light, a second harmonic of the light is generated by an optical crystal (45); and the second harmonic enters a photomultiplier (72). A photon counter 52 counts photons based on the output of the photomultiplier and calculates an average value of the count output.