The time-of-flight (TOF) principle is a well known technology to acquire a scene in all three dimensions. The advantages of the knowledge of the third dimension are obvious for many kinds of applications. The distance information within the scene renders automatic information-processing systems more robust and much less complex or even enables completely new solutions. A solid-state image sensor containing 124 × 160 pixels and the corresponding 3D-camera, the so-called SwissRanger camera has already been presented in detail 1 . It has been shown that the SwissRanger camera achieves depth resolutions in the sub-centimeter range, corresponding to a measured time resolution of a few tens of picoseconds with respect to the speed of light (c ≈ 3 · 10 8 m s −1 ).However, one main drawback of these so-called lock-in TOF pixels is their limited capacity to handle background illumination. Keeping in mind that in outdoor applications the optical power on the sensor originating from background illumination such as sunlight may be up to a few 100 times higher than the power of the modulated illumination, the sensor requires new pixel structures eliminating or at least reducing the currently experienced restrictions in terms of background illumination. Based on a custom 0.6µm CMOS/CCD technology, a new pixel architecture suppressing background illumination and/or improving the ratio of modulated signal to background signal at the pixel-output level was developed and will be presented in this paper. The theoretical principle of operation and the expected performance measures are described. Furthermore, test results obtained in a laboratory setup are published. The sensor structure is characterized in a high background-light environment. This in-depth evaluation leads to a comparison of the background suppression approach with the traditional pixel structure in order to highlight the benefits of the new approach.
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