# A Low-Cost Terahertz Camera
## 3 Results and Discussion
To do so, we used the signal level obtained from the integration of counts within the sensing area (e.g., an area covered by 100 \(\times\) 100 pixels in our case). As mentioned previously, using a pyroelectric detector from Gentec, model THz251-BL-BNC-D0, a THz energy of \(\sim\)3 \(\upmu\)J at 1 kHz repetition rate was measured, which corresponds to an average power of \(\sim\)135 \(\upmu\)W after attenuation  
Figure 3: (**a**) Compact Pro camera result of the THz beam spot imaging at the focus position after 5 Si wafers of attenuation (i) with its background information (ii) and the resulting background free image (iii). (**b**) IRXCAM-384 THz camera result of the same THz beam spot at the focus position using dynamic background subtraction function (i) with an extracted zone corresponding to the same sensor size as the Compact Pro camera. (**c**) Cross-section intensity profile of THz spot size obtained for both cameras. (**d**) Recorded background level using 8 bits resolution (limited by the software application) for the Compact Pro in a normal condition (i.e., box closed and chalcogenide lens) and after removing the chalcogenide lens and its framing box (i.e., for THz imaging capability). The profile of a saturated THz beam spot from the Compact Pro camera with 4 Si wafers of attenuation is also presented. by five silicon wafers. The noise level was calculated from the standard deviation of the fluctuations at each pixel. In Figure 4, we show an example of the noise fluctuations for a single pixel and for a \(100\times 100\) pixels area as a function of time (i.e., while targeting a uniform heat object consisting of a metallic cover). In this measurement, an acquisition frame rate of 9 Hz is estimated from the 90 images recorded in 10 seconds (i.e., also expected from the manufacturer specifications). It is clear from Figure 4 that the 8 bits resolution of the Compact Pro is not enough to resolve the noise fluctuations. Mainly, the thermal drift of the device is observed with sudden jumps whenever the mechanical shutter is activated (as seen by the averaging behaviors from the \(100\times 100\) pixels area). It is also clear from Figure 4 that the single pixel noise reading is numerically clipped as a function of time. Thus, our standard deviation evaluation does not provide the real limitation in sensitivity of Compact Pro camera. Nevertheless, from these curves, we estimated a conservative standard deviation of the fluctuations to be in the order of 0.5% of the full dynamic range. For a recorded area of \(100\times 100\) pixels, we found an integrated number of counts of 1,181,598, which corresponds to a 135 \(\mu\)W in THz power reading divided by the camera frame rate of 9 Hz. After subtracting the background information, a signal to noise ratio of 140 was estimated. This measurement indicates a NEP of about 100 nW for the Compact Pro camera in the 0.1 to 2.5 THz frequency range. This number is well above the \(<100\) pW of the IRXCAM-384 THz camera from INO [21], as expected for a scientific camera. Nonetheless, the Compact Pro camera offers a functional and affordable imaging capture device for the THz frequency range. A simple additional modification, such as changing the mechanical chopper to a synchronous background subtraction, would drastically improve its scientific value. Moreover, adding the capability to save the data in the raw format of the native 14 bits analog to digital converter would also bring this camera to another level, without large expense. In such a case, the signal resolution would be improved by a factor 64, and at the same time, the minimum detectable signal or NEP would be improved accordingly.