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 optical fiber focusing of a spectrometer often introduces a certain error, which measures biological tissue parameters inaccurate. In addition, the traditional single integrating sphere is bulky and inconvenient to carry. The single integrating sphere system needs to be assembled with optical fiber, which is inconvenient to operate. Repeated disassembly and assembly of the system also cause the optical fiber interface to loosen, thereby introducing 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 stepping motor, a single 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. The photomultiplier tube is used as a detector instead of a spectrometer to measure the diffusely reflected light from the sample passing through this small-scale integrating sphere. In this paper, we conducted an experiment with 7 subjects by this system to measure the diffuse reflectance spectra in vivo. 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.