In this paper, thermal expansion measurement of thermoelectric materials has been done using digital holography technique. In the experimental setup, a diode laser, a digital camera and a sample on a hot plate were put in the same alignment, so it is call Digital in-line Holography (DIH). A laser beam was expanded parallel and then propagated through a thermoelectric sample which would be heated by a hot plate from a room temperature to 224 °C. The images of a TE sample were recorded by a digital camera and analyzed data by numerical image reconstruction. From our experimental measurement result, thermoelectric material was expanded with temperature slightly, and its thermal expansion coefficient (COE) was found equal to α<sub>TE</sub> = 2.25 × 10<sup>-6</sup> °C<sup>-1</sup>.
In this paper we propose a modern technique to evaluate the shape changes of solder paste by using double-view in-line digital holography. We observed the transformation of three different kinds of solder paste composition: pure solder paste, solder paste mixed with 0.02%, 0.05%, 0.10% graphene (GPN) and 0.02%, 0.05%, 0.10% graphene oxide (GPNO), respectively. The shape of the solder pastes was investigated at different melt temperatures (i.e. 200°C, 250°C, and 300°C) for 30 seconds using a collimated beam propagating through the solder paste, then being double reflected on a mirror and second incident on another sides of the solder paste. The double images bearing beams were recorded with a CCD sensor simultaneously. The single recorded digital hologram from double view technique was reconstructed using digital holography. The results show that the double-view technique provides reliably data. Moreover, it would be developed for observing more than two images by single holography writing in the future.