Abstract: The invention pertains to an image processing device, in particular a device for stereoscopic image processing, and to a coherence detector used thereon. The image processing device can process stereoscopic images in real time and can be implemented with simple means and low expense. Two alternative embodiments of the coherence detector are disclosed. The image signals can be processed at the speed that they are supplied by image receivers, and thus image data processing is possible to attain depth information with little expense and in real time.