Skip to main content

STUDY AND REALIZATION OF A PHOTOREFRACTIVE HOLOGRAPHIC HEAD FOR REALTIME ANALYSIS OF VIBRATION

Objective


The main achievements can be summarised as follows:

- The crystal growth process has been studied, and the results allow a better prediction of the required settling of important growth parameters like rotation speed, pulling speed, temperature adjustment etc. during the manufacturing of photorefractive crystals for holographic purposes.

- The sensitivity of the photorefractive crystals has been increased for red light so that now, samples of sufficient sensitivity are available.

- The behaviour of the crystals during single pulsed and double pulsed operation has been studied so that the build-up process of the photorefractive grating (which shall be exploited) can be predicted.

- A new real-time determination of the interference phase has been developed and tested.

- A holographic recording head with a recording of the holograms on photorefractive crystals and a real time interference phase evaluation has been realised and tested.

- All requirements for the optical components and the electronic drivers and power supplies have been calculated, defined, produced, assembled and set into operation.

- A laboratory set-up has been assembled and tested.

- The required features of the image processing have been realised and tested.

- Theoretical studies for the validation of the adaptability of photorefractive crystals to the train pulse technique have been studied, an optical system has been set-up and tested with good results.

- The system prototype has been defined, assembled and successfully tested with a pulsed ruby laser on a vibrating object in industrial environment.
The objective of this proposal is to study and to realize a new concept of holographic interferometry for realtime investigation of vibrations.

Up to now, two states of de deformation of a dynamically stressed object are recorded on a hologram using pulsed lasers. These holograms have to be proposed before they can be read into an image processing system and the vibration analysis can begin. With the proposed project, a new image recording technique will be realized: photorefractive crystals with immediate response to the laser light will the place of conventional holograms, and a new principle of phase determination will replace the conventional phase shifting technique. It will thus be possible to record fringe patterns with double pulsed holography (pulse separation adjustable between 50 us and 800 us) on-line on a twin CCD sensor, which is connected directly with the evaluation system. Computerbased fringe analysis will allow to visualize and to quantify the object deformation. The interferometric realtime inspection system consists of the following devices:

- the photorefractive holographic recording head

- triggering and synchronisation unit

- fringe evaluation- and analysis system.

The new instruments can be employed in industrial environment and allows new applications in the field of research and development, nondestructive testing and study of material and design characteristics.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Labor Dr Hans Steinbichler
Address
Am Bauhof 4
83115 Neubeuern
Germany

Participants (3)

INSTITUT D'OPTIQUE THEORIQUE ET APPLIQUEE
France
Address
Centre Scientifique D'orsay , Bètiment 503
91403 Orsay
PRAME
France
Address

33165 Saint-medard-en-jalles
PSA PEUGEOT CITROEN
France
Address
Route De Gizy
78140 Velizy-villacoublay