SensArray Infrared Corp., a manufacturer of lead salt infrared imaging products and host materials for mid-infrared lasers, said it has completed a new equity investment from Digital Power Capital LLC of Greenwich, Conn. SensArray Infrared also recently joined with BAE Systems, of Nashua, N.H., in a licensing agreement to develop processes for commercial and military applications.    . . .   Alliance Imaging Inc., a provider of outsourced diagnostic imaging services, announced that its chairman, CEO and founder, Richard Zehner, will assume the sole role of chairman of the board and that Paul Viviano has been named CEO. Andrew P. Hayek will join Alliance as executive vice president and COO.