Evaluation of handwriting peculiarities utilizing laser speckle contrast imaging

Functional handwriting is a process involving various complex interactions between physical, cognitive and sensory systems. Since muscular motion is of a peculiar nature for each person, handwriting properties, such as pencil pressure and speed of writing, can be considered as a unique marker of identity. Moreover, impairments of handwriting in many cases are connected to neurodevelopmental disorders such as attention deficit hyperactivity disorder, developmental coordination disorder, autism spectrum disorders, Parkinson's disease, etc. From this point of view, investigations of handwriting kinematics and pressure can be highly important for both forensic science and medicine. Commonly, the kinematic and pressure features of handwriting are evaluated using a graphics tablet with a stylus or electronic pens. The production of such devices is quite expensive. Therefore, the development of new methods for individual handwriting analysis is an important and current goal. Laser speckle contrast imaging (LSCI) is a powerful method, which is sensitive to both motion and pressure. Since the developed technique requires the use of only a simple laser diode and camera for image acquisition, LSCI is a cost-effective and practical tool for handwriting analysis. In the current letter we present a robust LSCI-based method for handwriting pressure and kinematics evaluation. The introduced approach was validated by an Archimedean spiral writing task.