Diffuse reflectance spectra measurement in vivo skin tissue based on the integrated single integrating sphere system

The single integrating sphere combined with a spectrometer is often used to measure the diffuse reflectance spectrum of biological tissue. However, the traditional single integrating sphere is bulky to carry. Besides, the single integrating sphere needs to be assembled with an optical fiber of the spectrometer, which is inconvenient to operate. Repeated disassembly and assembly of the system can also lead to loose fiber interfaces, which can introduce errors. In this paper, we proposed an integrated single integrating sphere system to measure the diffuse reflectance spectrum of biological tissues in vivo. The integrated single integrating sphere system is composed of a broad-spectrum light source, a beam-splitting system, a small-scale integrating sphere, and an extended photomultiplier tube. The small-scale integrating sphere is convenient to carry, which can accurately and quickly collect the diffuse reflected light of the sample tissue. The photomultiplier tube is used as a detector instead of a spectrometer to measure the diffusely reflected light from the sample tissue passing through this small-scale integrating sphere. In this investigation, we measured the in vivo diffuse reflectance spectra of 7 subjects based on the system. We also used the Monte Carlo algorithm to verify the measurement results of the diffuse reflectance spectra. The Monte Carlo simulation results show that the system can achieve the in vivo non-invasive measurement of the diffuse reflectance spectra of biological tissues.