Holography

Introduction

What’s holography?

From escalator of MRT CKS memorial hall station.

Introduction

A method of obtaining three- dimensional photographic images. These images are obtained without a lens, so the method is also called lensless photography. The records are called holograms. Invented by the British physicist Dennis Gabor in 1947.

British physicist Dennis Gabor won the Nobel Prize in physics in 1971.

Ordinary photograph is 2D recording of a 3D image.

Holography is a 3D recording of a 3D object.

In photograph only the intensity variation of light is recorded.

In holography the intensity as well as the phase variation of the light is recorded

The recorded photographic film is called a hologram

Comparison between

photography 2D image of 3D object Intensity variation only

recorded Recorded film is called

photograph Point to point recording of

the intensity of light When cut into pieces, each

piece gives partial information only

holography 3D image of 3D object Intensity and phase

variation recorded Recorded film is called

hologram Each point of the film

receives light from all parts of the object

Each piece gives full information of object

photography Lenses are needed There is resemblence

between object and image(photograph)

Only single image can be recorded on a film

Information capacity is less

holography Lenses not needed Holograms have no

resemblence to the objects recorded

Several images can be recorded on a film

Information capacity is much more.

Basic principle

Recording of a hologram (construction)Reconstruction

Recording of a hologram

Recording of Hologram

Laser light is split into two by a beam splitter

One part is incident directly on the film (reference beam)

Other part is incident on the object. The diffracted wave from the object(object wave)is incident on photographic film.

These waves superimpose on the film and hologram is recorded.

Reconstruction

Reconstruction

Hologram is illuminated with the same kind of light as reference waves

2 images will be producedOne is virtual image-this can be viewed

in 3D form with all the characteristics of the object

Another is real image- which can be obtained on a screen and photographed.

Applications

1. Holographic image formation

2. Fog droplet camera

3. Dynamic aerosol camera

4. Interferometry- to study the distribution of strain on objects using double exposure holographic interferometer

5. Holography used for character recognition-applied to identify finger prints

Applications

Holographic gratingsUsed in computer memories-with very

high storage capacity In bio medical science- for the NDT of

artificial heart valve.Acoustic holographyHolographic Microscopy

Application

3D picture: