Compact FT Spectrometers

Applications

The Inventors have developed a compact Fourier Transform (FT) spectrometer for analyzing the intensity of electromagnetic radiation, ranging from UV to infrared, as a function of its spectral composition. This micro-device is suitable for smartphone-integrated FT spectrometers, and as such drastically lowers the threshold for using FT spectroscopy in daily life. Smartphone spectrometers can be used for such tasks as detecting blood sugar or blood oxygen levels and measuring UVA levels to determine cancer risks, among numerous other spectroscopic tasks across commercial, industrial and scientific domains.

Problem Addressed

This invention addresses numerous shortcomings of conventional FT spectroscopic approaches that are less readily adaptable to devising a compact device, e.g. for use in smartphone spectroscopy. One problem with traditional spectrometers is that they contain dispersive elements, like gratings or prisms, which limit the spectral bandwidth of the device. The Inventors’ device does not require the filtering of wavelengths and can be tailored to work throughout the spectral bandwidth set by the detector that can typically be an order of magnitude. In traditional devices, these gratings are generally used off-axis in either transmission or reflection modes. In comparison, the Inventors offer a transmission setup offering the advantages of having all optical components on the optical axis. This results in low optical aberrations and thus compact systems with minimum number of optical elements. Additionally, their spectrometer system does not require a high degree of collimation, thus allowing for short focal length collimators that enable smaller, compact devices.

Technology

The Inventors’ compact FT spectrometer is comprised of the following optical components: an entrance aperture, a collimating lens, a transmissive or reflective phase shifter array, a focusing lens and a zeroth diffraction order selecting exit aperture. The entrance aperture limits the incident radiation flux. The collimating lens, referred to as the micro-phase-shifter-array (MPSA), is focused on the entrance aperture, while a second lens focuses a parallel beam onto the exit aperture and simultaneously projects an image of the MPSA onto an array detector. The array detector records the pixelated interference pattern and sends is pixel information to a CPU computing the spectral composition of the input radiation via Fourier-transformation or matrix inversion. The device utilizes a specific optical configuration and shape of the MPSA, as well as a specific focal distance between the focusing lens and the exit aperature, that allows spatial filtering of higher diffraction orders.

Advantages

  • System design minimizes number of optical elements needed
  • Spectrometers are highly compact and portable
  • Devices can be used with smartphone cameras, making them highly accessible to everyday spectroscopic uses across commercial and industrial domains