2.1 - Multi-Wavelength Digital Holography for 3D-Shape-Measurements on Rough Surfaces

Fast and accurate Measurement of the 3D shape of objects with rough surfaces is a demanding task. We present a novel sensor for non-contact 3D-imaging based on digital holography. For this task up to six stabilized diode lasers emitting light of slightly different wavelengths are employed to illuminate the object. For each of the wavelengths three holograms are recorded with a CCD-Camera (1000 x 1000 Pixels). The hologram acquisition is permformed without an imaging lens. From the recorded holograms the optical waves in the plane of the object under investigation at each of the wavelengths is reconstructed numerically using a consumer grade graphics processing unit. As a result of the reconstruction process the amplitude and the phase of the optical waves in the plane of the object are known. The differences of the measured phase values in each of the reconstucted object points allow for the meaurement of the threedimensional shape of the object. The field of view of the presented sensor is set to 20 mm x 20 mm. The field of view can be adjusted to other values by changing the object illumination path of the optical setup. The axial measurement range is more than 10 mm with an axial resolution of less than 5 µm. The overall time for data acquisition and evaluation of the three-dimensional shape is approximately 1,6 seconds. Besides a detailed description of the sensor we present results of measurements of typical objects in the field of automotive industries and elctronic devices