It is shown that a roof Dove prism is a typical circular beam deflector used in a transmitted parallel beam, Apparently, the importance of this prism is for its multifunction. However, it is unfavorable because of its high value of length-aperture ratio, which imposes restrictions on extending its application to many cases, To overcome the difficulty, a new type of roof Dove, i.e., a square-sectional roof Dove prism and its arrays are developed to reduce greatly the length-aperture ratio. In addition, Dove prisms are used in a certain kind of series of two to form a circular beam deflector, Arrays in the same kind of series also greatly reduce the length-aperture ratio. The potential of these new types of reflecting prisms and prism arrays will rely on the development of fabrication techniques as well as on further research. (C) 1996 Society of Photo-Optical Instrumentation Engineers.