Digital holographic cameras

Optomechatronics cameras based on digital holography and grating interferometry are presented. Their compact design, "black box" operational approach and interferometric data processing are described. The representative Fast growing technology and requirements for testing of different types of materials and devices require new methods and systems for investigation of their parameters in laboratory, workshop and outdoor conditions. Main interesting quantities are: shape and shape deformation, local materials constants and displacement/strain distributions. Several optical techniques have been already developed for these measurements [1]. One of them is holographic interferometry and in particular its digital version (DHI), which provides a simple way to record and restore amplitude and phase of an investigated object [2]. It allows, using amplitude information, distant monitoring of object and remote optoelectronic reconstruction.

Proper manipulation displacement during loading. Other technique, developed for in-plane displacements/strain measurement and monitoring, is grating interferometry
(GI) [3]. In the paper a new optomechatronics cameras based on both, DHI and GI, techniques are introduced. Those cameras systems with compact design and "black box" measurement approach allow fast and accu- Digital holography provides a way to record and restore amplitude and phase of investigated object [2]. It allows, using amplitude information, distant monitoring of object and remote optoelectronic reconstruction. Proper manipulation of phase could provide information about shape of an object and its out-of-plane and in-plane displacements during internal or external loading.

The architecture of holographic system (Fig.1) which consists of two types of measurement heads, fibre optics link and control/illumination module is presented. One of the measurement head is configured to perform out-of-plane displacement and shape measurement. The second one (with four illumination beams) allows to measure (u,v,w) displacement fields. The data from both cameras can be transferred remotely to optoelectronic reconstruction station based on LCOS spatial light modulator.

Due to fibre optics light delivery system the DHI head is able to work in a distance from itselectronic/processing part and it allows direct access to all mechanical parts of machinery. The DHI head can be hand-held or can be mounted directly at a machine.  In practice two main configurations are applied depending on the choice of measurand, namely: the out-of-plane displacement/shape measurement setup and full displacement vector (u,v,w) setup. The hardware and software user friendly cameras for industrial inspection two separate devices  have been designed and built: DH_SHAPE and DH_UVW. All the optical elements and detector are closed in a tube with the diameter 50 mm.


The source is pigtailed laser with output power 7mW and operating wavelength beams respectively. The tip of object illumination fibre can be subjected to the linear shift introduced by micromotor. Reference fiber tip is placed in the focal point of collimator lens and the plane reference beam directed through mirror and beam splitter is impinging at CCD matrix. beamsplitter cube and the resultant interference field is captured by CCD matrix. The CCD is the standard microhead B/W camera JAI M536 CCIR with pixel size 8.6 ?m and resolution 752x582 pixels. The dimensions of measurement head are: diameter 50mm and length 100mm.