In this paper we present a new method to achieve quantitative phase contrast imaging in Digital Holographic Microscopy (DHM) that allows to compensate for phase aberrations and image distortion by recording of a single reference hologram. We demonstrate that in particular cases in which the studied specimen does not have abrupt edges, the specimen’s hologram itself can be used as reference hologram. We show that image distortion and phase aberrations introduced by a lens ball used as microscope objective are completely suppressed with our method. Finally the concept of self-conjugated reference hologram is applied on a biological sample (Trypanosoma Brucei) to maintain a spatial phase noise level under 3 degrees.

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Total aberrations compensation in digital holographic microscopy with a reference conjugated hologram

A holographic lens has been made that utilizes some of our earlier work on holographic aberration correction [ J. E. Ward D. C. Auth F. P. Carlson , Appl. Opt.10, 896 ( 1971)]. The lens properties are obtained by interferometrically recording a plane wave and a pinhole generated spherical wave. The theoretical analysis is followed by the results of the Ronchi lens test, Fourier transformation of a grating, and imaging of a test picture.

Holographically generated lens.

Chromatic and spherical aberration of Fresnel-zoned diffraction gratings may be of the opposite sign and the same magnitude as for glass lenses. This peculiarity is used to improve the stigmatism of single glass lenses in polychromatic radiation. Two types of compensation gratings are studied: point holograms reconstructed out of stigmatic conditions and holograms of the aberrating wave surface itself, reconstructed in the conjugate order.

Holographic correction of both chromatic and spherical aberrations of single glass lenses.

A means for optically coupling a semiconductor laser to an optical fiber is disclosed. In one embodiment, a volume phase holographic element is disposed on a light-emitting surface of a semiconductor laser. The volume phase holographic element acts as an aberration-corrector for a lens that is disposed between the semiconductor laser and the optical fiber. In this way, an inexpensive lens that is not aberration free can be used. In some embodiments, the volume phase holographic element converts a Gaussian light beam emitted by the semiconductor laser into an annular beam that is more suitable for long distance transmission in multimode fibers.

Transmitter optical subassembly with volume phase holographic optics

An inexpensive, high quality transmissive holographic optical element and method for making same are described. The holographic optical element consists of a potentially aberrating substrate which supports a layer of holographic recording material. The material contains a recorded fringe pattern that cancels the aberrations induced in an image wavefront as it passes through the aberrating substrate. This optical element is formed by a method having the following steps. A first wavefront from a source, for example a point focus, is passed through the aberrating substrate, becomes distorted, and then passes through the holographic recording material to a wavefront conjugator. The conjugator launches a conjugate of the distorted wavefront back to the holographic recording material. A second wavefront is then passed through the holographic recording material to form a fringe pattern or hologram as a result of the interference of the conjugate waveform and the second waveform. Subsequently, the developed holographic optical element is illuminated with a reconstruction wave which is the duplicate of the reference wave. Passage of this reconstruction wave through the holographic layer results in an emerging wavefront identical to the conjugated distorted wavefront which is then converted to the original wavefront as it passes through the aberrating substrate.

Transmissive holographic optical element on aberrating substrate

The correction of lens aberrations using a hologram made with a collimated reference is discussed. Two geometries in which the theoretical third-order hologram aberrations may be avoided are demonstrated. The results of experiments which demonstrate the aberration correction using the Ronchi and DeVany tests are presented.

J. E. Ward

Papers

Lens Aberration Correction by Holography