Miniaturized sensor head for distal holographic endoscopy

In this paper we describe a miniaturized sensor head based on digital holography for endoscopic measurements. The system was developed to measure the shape and the 3D-deformation of objects which are located at places that cannot be accessed by common measurement systems. Therefore, a miniaturized optical sensor including a complete digital-holographic interferometer with a CCD-camera is placed at the end of a flexible endoscope. The diameter of the head is less than 10 mm. The system enables interferometric measurements with a speed of three reconstructions per second and it can be used outside of the laboratory in a usual environment. Shape measurements are performed with two wavelength contouring, while the deformation is measured with digital holographic interferometry. To obtain full 3D-data in displacement measurements the object can be illuminated sequentially from three different illumination directions. To increase the lateral resolution temporal phase shifting is used.