DSW700 System Description

DSW700 Technical Details

Overview

Softcopy photogrammetry work, stereo-compilation, and ultimately, orthophotos can

only be as accurate as the source imagery. Working in a digital photogrammetry environment requires that the scanned aerial photographs are not only as accurate as possible but that the appearance of the film is reproduced faithfully and that the raw air photos are scanned quickly so that production can begin rapidly.

The Leica DSW700 Digital Scanning Workstation is a photogrammetric scanner,

designed for maximum throughput. It is capable of scanning aerial film, cut sheets or roll, black and white, color or false color, positive or negative, at a very high speed. The geometric and radiometric performances meet all photogrammetric requirements. The DSW700 includes several innovations, not only to achieve maximum speed but also to optimize radiometric performance by virtually eliminating Newton rings.

The DSW700 is built on the successful design of the earlier DSW200/300/500/600 models, based on a heavy, precise mechanical construction with moving stage plate, and stationary digital camera with state-of-the-art CCD sensor. The principal improvements over current scanner design include a novel ring light with LEDs of various colors, a high quality 11-megapixel sensor, and anti-reflective coatings on the stage and cover plates to combat Newton rings. A further innovation is the use of next generation optical encoders to position the stage, resulting in increased geometric accuracy.

Key Features

The Leica DSW700 Digital Scanning Workstation performs precision scanning of black and white, color or false color, cut or roll film negatives and diapositives at a very high speed, to provide the highest quality digital imagery for use in softcopy photogrammetric workstations.

The system consists of the following principal components:

∙Heavy mechanical construction, with stage plate mechanism, to support the motorized roll-film transport, moving in the X and Y directions below the stationary illumination source and above the lens and sensor

∙Dome light source consisting of LEDs of different colors

∙12-bit CCD large-array sensor to capture the image patchwise

∙Convenient change of optical pixel size throughout the full 3µm to 20µm continuous resolution range, so that scanning takes place at the pixel size required by the user, without any image resampling

∙High performance PC host computer running Windows® XP Professional

∙Comprehensive, flexible software to control all aspects of the scanning operation, facilitated by an easy-to-use graphical user interface.

The XY stage is built to very high mechanical standards, taking into account that both cut and roll film must be accommodated. The stage is exceptionally sturdy and provides independent positioning with respect to the X and Y sensor axes. Mounted on the base are the optics and 12-bit digital sensor used to digitize the transparencies. The optical path has been minimized for optimal performance: no beam splitters or folding mirrors are used and the light path is straight. The stage and optical path are mounted inside a specially designed enclosure, which prevents dust and dirt from accumulating on the film or extraneous light from entering the system during scanning. Illumination is provided directly by an LED dome light supported above the stage. This cool light source is located 125 mm above the platen, so does not subject the film, stage or optical path to unwanted heat. The dome consists of LEDs of different colors to allow for color as well as black and white images to be scanned.

gi.leica-geosystems.com