Terahertz spectroscopy and imaging in dynamic environments

A system comprising:

• a transmitter configured to emit a continuous electromagnetic (EM) wave in a terahertz (THz) frequency band into a dynamic environment, the dynamic environment including a transmission medium that changes over time;
• a receiver configured to receive a reflected EM wave from at least one object in the environment;
• one or more processors;
• memory storing instructions that when executed by the one or more processors, cause the one or more processors to perform operations comprising:
• determining a spectral response of a received signal indicative of the reflected EM wave, the spectral response including absorption spectra at a frequency in the THz frequency band that is indicative of the transmission medium in the environment;
• compensating, by the one or more processors, the spectral response by:
• determining a trend line representing an average signal strength of peaks in the spectral response of the received signal;
• and
• subtracting the trend line from the spectral response of the received signal;
• comparing the absorption spectra with known absorption spectra of target transmission mediums;
• identifying a particular target transmission medium as being the transmission medium in the environment based on results of the comparing;
• determining a concentration level of the particular target transmission medium in the environment, wherein determining a concentration level of the particular target transmission medium in the environment, further comprises:
• determining an absorption loss from the absorption spectra in the spectral response of the received signal;
• determining a path length of the received signal;
• and
• using the absorption loss and the path length to obtain the concentration level of the target transmission medium in the environment.

A non-transitory, computer-readable storage medium having stored thereon instructions that when executed by one or more processors, cause the one or more processors to perform operations, comprising:

• emitting an continuous electromagnetic (EM) wave in a terahertz (THz) frequency band, the EM wave being emitted into a dynamic environment that includes a transmission medium that changes over time;
• receiving a reflected EM wave reflected off at least one object in the environment;
• determining a spectral response of a received signal indicative of the reflected EM wave, the spectral response including absorption spectra at a frequency in the THz frequency band that is indicative of the transmission medium in the environment;
• compensating, by the one or more processors, the spectral response by:
• determining a trend line representing an average signal strength of peaks in the spectral response of the received signal;
• and
• subtracting the trend line from the spectral response of the received signal;
• comparing the absorption spectra with known absorption spectra of target transmission mediums;
• identifying, based on results of the comparing, a particular target transmission medium as being the transmission medium in the environment;
• and
• determining a concentration level of the particular target transmission medium in the environment, wherein determining a concentration level of the particular target transmission medium in the environment, further comprises:
• determining an absorption loss from the absorption spectra in the spectral response of the received signal;
• determining a path length of the received signal;
• and
• using the absorption loss and the path length to obtain the concentration level of the target transmission medium in the environment.