Photon Dynamics Inc. has named Jeffrey A. Hawthorne as senior vice president to manage its flat-panel display business. He replaces Bernard T. Clark, who has resigned.   . . .   Provectus Pharmaceuticals Inc. announced it has received US patent No. 6,519,076, covering signal encoding and processing methods that can increase the sensitivity of imaging systems used in biomedical research. Provectus scientists said the methods can be used to enhance the performance of a variety of microscopy systems used in clinical and research laboratories.