Real-time transmission-type terahertz microscope with palm size terahertz camera and compact quantum cascade laser

Abstract

This paper describes a real-time transmission-type Terahertz (THz) microscope, with palm-size THz camera and compact quantum cascade laser (QCL). The THz camera contains 320x240 microbolometer focal plane array which operates at 30 Hz frame rate and has lock-in imaging function as well as integration functions such as frame integration and spatial filter. These functions are found very powerful in improving signal-to-noise ratio. QCL is installed in compact Stirling cycle cooler. A variety of QCLs covers frequency range from 1.5 to 5 THz and provides time-average power of 0.5~2 mW. The illumination area for sample is changed by adjusting one lens in the illumination optics. Performances of the THz microscope, such as signal-to-noise ratio and so on, were measured and are found consistent with the calculations. THz images taken with the THz microscope are finally presented.

Fast 2-D and 3-D Terahertz Imaging With a Quantum-Cascade Laser and a Scanning Mirror

“…The shape of the blade is easily recognizable. Note that there is no fringe pattern in the image, which is often observed in images obtained when using a detector array [19], [22]. In Fig.…”

“…Real-time imaging with a QCL was realized using a commercial focal-plane array microbolometer camera for detection [19]- [22]. However, these systems seem to suffer from fringe patterns, which appear in the THz image.…”

“…However, these systems seem to suffer from fringe patterns, which appear in the THz image. These are caused by diffraction, etalon effects, and interference [19], [22].…”

Technology trend in real-time, uncooled image sensors for sub-THz and THz wave detection

“…It is found in Fig.9(b) that the lock-in imaging function increases SNR as a function of square root of the number of frame-integration, while frame integration without lock-in function does not so much increase SNR as expectation, because low frequency noise is predominant in microbolometer FPAs. [41] . Figures 11(a) and (b) show THz images of tablet put into an envelope and metallic clip put under flours, respectively.…”

Compressed Sensing in a Fully Non-Mechanical 350 GHz Imaging Setting

“…Such imaging systems are already built on commercial basis and can be used for specific practical tasks [19]. Judged by their noise equivalent power (NEP), a single pixel of such a detector array (typical NEPs are spanning from 10 -9 W Hz -1/2 [19] over 10 -11 W Hz -1/2 [20] up to 0.5 10 -12 W Hz -1/2 [21]) is less sensitive than very sensitive single-pixel detectors (typical NEP~10 -14 W Hz -1/2 [22]). Some detectors used for space applications do have even lower NEPs (e.g.…”