Dell O. Fystrom
Phys. Dept., Univ. of Wisconsin, LaCrosse, WI 54601
Thomas D. Rossing
Northern Illinois Univ., DeKalb, IL 60115
Holographic interferometry is widely used to determine the modes of vibration in a wide variety of objects, such as musical instruments. Use of two or more object beams is a convenient and inexpensive way to increase the depth of field (or coherence volume) in holographic interferometry. This technique was used, for example, to make time-average holograms of the inside and outside surfaces of a vibrating drum shell simultaneously.