Optical improvement of the dynamic laser speckle for seed analysis using portable digital camera

The biological activity assessment using the dynamic laser speckle (DLS) technique is recognized as a feasible methodology to analyze seeds vigor. Nevertheless, the technique presents the accessibility as a restriction to final users, and the large size of the equipment is a key limitation to allow the portability of the DLS. This work aimed to propose a reduced and portable configuration of the image capture system adopted in the DLS technique for seed analysis applications. A compacted digital camera with an embedded magnification, known by mini microscope, was tested associated with adapted diaphragm as an alternative to the traditional CCD camera, macro zoom and integrated diaphragm. The tests of the proposed adapted mini microscope, in comparison to the traditional configuration, were carried out in the monitoring of drying a paint and in the separation of high-vigor from early-aged seeds. Diaphragms with three different apertures (3, 4 and 5 mm) were evaluated. The results using the 3 mm diameter aperture presented the best performance, like in the case of the traditional CCD camera set. It was possible to follow the drying of a paint activity compared to its loss of weight and to distinguish statistically high-vigor from early-aged seeds at a significance level of 5%. The reliable results of the proposed configuration offered a compact and portable version for using the DLS in seed analysis laboratories.