Utilisation_of_Computers_in_Holographic_Interferometry

3.6 Utilisation of Computers in Holographic Interferometry

In the case of the experiments utilizing holographic interferometry either with transparent (phase) objects or with solid (diffusively reflecting) bodies the first thing to be done is the record of the holographic interferogram. If necessary the image is modified by various techniques and, finally it is qualitatively and quantitatively analysed. Nowadays, in all the phases computers with particular hardware and software (Csongrády, 1996) are successfully used to supply the slow and routine activities by automatic calculation, which considerably simplifies the processes and analyses of the experiments.

At present, during the experiments in the field of holographic interferometry the classical photographic or digital recordings of images are used.

The advantage of classical photographic recordings is the high resolution of the recording medium and its relatively good sensitivity. Because of the complicated processing this method of recording is gradually replaced by digital recording.

Two-dimensional digital record of the object can be obtained if we display three-dimensional objects by means of lenses, for example to the plane of the CCD camera sensor, or we can create it by optical and mechanical resolution of the image, or by digitalisation of analogue image signals through digitising computer cards, or by digitalisation of photographic records by means of a scanner we can transform two-dimensional photographic patterns into two-dimensional digital recordings that are later stored in the form of computer (image) files.

The advantage of digital recordings is the possibility to transmit and copy them without noises thus eliminating their complicated development by so-called wet way necessary in the case of classical photographic recordings. Digital recordings allow immediate processing and analysis of images in computer, which markedly makes the research more efficient by holographic-interference methods. The disadvantage of even high quality digital recordings by either digital cameras or cine-cameras is their lower resolution and high actual price.

To make digital image recordings we need digital cameras with accessories as well as cards to connect the cameras to computers and special software for CCD cameras with either analogous or digital output.