We describe a digital holography technique that, with the simplicity of an in-line configuration, produces holograms where the real and virtual images are completely separated, as in an off-axis configuration. An in-line setup, in which the object is imaged near the sensor, is modified by placing a shifted knife-edge aperture that blocks half the frequency spectrum at the focal plane of the imaging lens. This simple modification of the in-line holographic configuration allows discriminating the virtual and real images. As a fluid velocimetry technique, the use of this aperture removes the minimum defocusing distance requisite and reduces the out-of-plane velocity measurement errors of classical in-line holography. Results with different test objects are shown.
© 2014 Optical Society of America
Original Manuscript: February 24, 2014
Revised Manuscript: April 9, 2014
Manuscript Accepted: April 28, 2014
Published: May 30, 2014
Virginia Palero, Julia Lobera, Nieves Andrés, and M. Pilar Arroyo, "Shifted knife-edge aperture digital in-line holography for fluid velocimetry," Opt. Lett. 39, 3356-3359 (2014)