Tetrahertz (THz) imaging is an attractive alternate to ultrasonic based Non-destructive Evaluation (NDE) especially for Fiber Reinforced Polymers (FRPs) such as Glass FRP (GFRP) composites as the latter demands proximity and additional coupling medium for the best performance. Typically, THz imaging system uses a single emitter-detector configuration employing raster scan method for image acquisition. The image acquisition speed is greatly limited by the speed of the mechanical stages and hence its usage in real-time industrial NDT applications such as in-line quality control has been limited. Alternatively, having an array of detectors will significantly increase the system cost. As an optimal compromise for speed and cost, line scanners are highly desirable. In this work, rapid imaging performance of a THz line scanner has been studied by imaging closely spaced defects in GFRP composites using a 100 GHz source. The total acquisition time for imaging the GFRP sample of dimensions 55× 35 mm² is 10 s, which is >100 times faster compared to a conventional raster scanning technique. In addition, image deconvolution techniques such as Lucy Richardson and Weiner deconvolution have been adopted to improve the quality of the acquired THz images. The results show that the THz line scanners can successfully be employed for rapid defect detection in GFRP composites.