Large Format Monochrome Scanners Explored
by Don Beauvais & David J. Wilson
Updated 2-04
Table of Contents
Sales of large format scanners have risen markedly over the last three years. Two reasons stand out for this rise in sales: the introduction of "low cost high quality" scanners and "low cost feature rich" editing software.
Scanner manufacturers have been able to cost reduce their products while making enhancements. Software companies have been able to capitalize on their years of research and development and incorporate these capabilities into high performance but affordable packages.
The highest growth years for scanners are yet to come as sales are driven by an increasing acceptance of applications derived around the capture of existing engineering archives. With an estimated 3% of engineering archives now in digital form, the market is projected to grow well into the 21st century.
Market Analysis
 According to studies conducted by Document Management Technology, the market for large format scanning systems within the EDM environment is modeled as shown in the graph. Low volume sales were realized throughout the 80’s until critical pricing barriers were broken and market dominant raster applications were readily available, starting in 1989.
In the past few years the scanning industry has gone through significant growth. This can be attributed to an increasing acceptance of low image quality applications in electronic drawing management and raster-based drafting. This explosive software growth was supported by the introduction of the first large format scanner at less than $20,000 by Contex Business Systems. As price erosion continues, scanner vendors will tend to differentiate their products with software features, platform/format support and scanner speed.
Scanning - An Introduction
What is a Scanner?
Scanners are similar to fax machines in that they both scan then create images via raster data. A fax machine sends raster data across phone lines while a large format scanner creates a raster file.
However, that is where the similarities end. Scanners are able to scan different types of media such as paper, sepia, vellum and transparencies. Many of these images are old and in poor condition which creates a challenge for even the best scanners.
How Does It Work?
A scanner contains an electronic camera and a light source. The drawing is fed through the scanner and the details are seen by the camera then saved as an electronic file. A raster (or bit-map) file is created.
Thresholding:
Because of the demands for high image quality when scanning technical drawings, scanners have a contrast setting called thresholding. This allows for the scanning of poor quality documents by distinguishing between the faded, dirty background of the document and the actual drawing or foreground information.
Accuracy:
The accuracy of a scanner is measured in Dots Per Inch, or DPI. This is the number of pixels, or dots, that the scanner sees for every inch of paper. The higher the DPI means more dots are produced creating a more accurate scan.
Resolution:
Two types of resolution are quoted by scanner manufacturers, optical and interpolated. Optical resolution is the true resolution of the scanner. Interpolated resolution is an increased resolution derived by software. When assessing resolution needs, pay attention to the optical resolution. Optical resolution can be calculated by dividing the scan width into the total number of CCD pixels.
Scanners are available in a variety of resolutions. The following is a general guide to help determine resolution requirements depending upon application:
Application Optical Resolution Requirement
Archival: 200 DPI
Raster Editing: 200 - 300 DPI
Raster to Vector: 300 - 400 DPI
GIS Conversion: 400 - 600 DPI
Technology:
Two types of imaging technology are being used today, CCD (Charged Coupled Device) and direct contact array. The most widely used scanning technology is the CCD. In an effort to reduce the cost of scanners, some manufacturers have adopted the direct contact array which is the same imaging technique used in fax machines.
High image quality with speed is the goal for scanner manufacturers. This has been more of a challenge for devices using direct contact array technology. Direct contact arrays use a limited LED source with a one-piece array while CCD technology links together multiple arrays. Advances with fiber optical sources are helping to eliminate this deficiency, but superior images at higher speeds are more easily accomplished with CCD technology. This is largely due to the usage of full spectrum light sources. Multiple CCD units require calibration or alignment that can effect the integrity of the scan if not properly aligned. Multiple CCD units also offer the advantage of creating higher "optical" resolutions.
Although very rare, in the event that your scanner light source needs to be replaced, it is much more expensive to replace the entire LED panel versus one CCD.
Raster File Types:
There are a wide range of standards and formats for raster files. File types can be split into two broad types, compressed and uncompressed. Compressed files are, as the name implies, much smaller than uncompressed files. Some common compressed file formats are Group 3, Group 4 and TIFF Compressed. Common uncompressed formats are PCX, RLC and TIFF Uncompressed.
There are also several standards used by government and military organizations such as the CALS standard used by the US Navy. These standards are usually applied to existing formats producing file types such as CALS Group 4.
Compression Methods:
Data compression techniques have evolved along with computer software and hardware. It is now possible to store a scanned E size drawing in equal or less space than the equivalent CAD drawing. The most popular compressed formats are the CALS raster and TIFF formats, both of which use the CCITT Group 4 compression method.
Raster Files vs. Vector Files:
CAD systems use vector files and scanners produce raster files. Raster files are fundamentally different from vector files. If you draw a circle with your CAD software, it is stored as a circle. The software knows the radius, line thickness, line type and center point. The circle is "intelligent" because any part of the circle "knows" that it is part of the circle and ‘knows’ what the rest of the circle looks like.
The raster file created when a drawing is scanned consists of many individual dots or pixels. The scanned image is "dumb" because the pixels form a shape but each pixel does not "know" that it is part of the shape.
Current Scanner Vendors
Contex
The standalone scanner market is dominated by Contex Business Systems, with an estimated 80% worldwide market share. They are the pioneers of low cost scanners introducing the first units to break the $20K and $10K price barrier. In 2001, the company acquired Vidar Scanners, then number 2 in the market, making it by far the largest scanner manufacturer in the world.
Product distribution is via their own international distribution network and two master distributors within the US (Ideal and Vemco). OEM relationships exist with OCE (standalone units line), Hewlett Packard (printer/plotter units) and CalComp (Scanplus III line).
Contex presently offers a full range of large format scanners with configurations bundled as 300, 600, 800, 1200, and 1800 dpi (interpolated). These scanners also have a color capabilities as well as black and white. The more recent models moved away from the top loading feed system to a front loading straight paper path approach.
Software and peripheral compatibility have played a key role in Contex’s success in the market. Their software control package (CADImage/SCAN) can interface with over 50 different raster formats ensuring compatibility with the outside world. CADImage/SCAN software has the same look and feel between platforms and is able to plot to a variety of output devices.
The Scanners do not include the stand.
Advantages:
Product runs in multiple computer environments
Largest installed base
Consistent scanner application across product lines
Strong compatibility position
Can be used on a table-top or with a floor stand
Excellent international distribution and support network
Solid scanner controller software
Vidar
Vidar Corporation possessed a solid second place for large format scanner sales worldwide until the acquisition by Contex. All of the Vidar manufactured scanners were replaced by Contex units.
The scanner software is robust and easy to use. It even has a feature that can automatically deskew scans. Scan speed is compromised when using this feature. It is better to feed the original in straight from the beginning.
The interface is included with the purchase of a scanner. All models include 2 year Return to Depot warranty with optional on-site service available.
Advantages:
Good domestic market presence
Automatic document locator
Automatic deskew
Excellent image enhancement circuitry
Fast!
Performance upgradeable with the Select family
Same units as Contex family
Action Imaging:
Action Imaging is the combined business of Colortrac and Anatech scanners. Both were acquired/merged over the past few years to offer a comprehensive line of color units. High end units with very wide scanner widths target specific GIS/Mapping markets.
Advantages:
Solid scanning software
Quality construction
Price
Worldwide service and support
OCE:
Oce uses the Contex scanner engine for their standalone models (please see section 4.1 for additional information). OCE scanners are unique to the Contex scanners in that they have an integrated stand and a paper path that allows for documents to be fed in from the front rather than from the top of the scanner. Oce also offers a multi-function product that integrates plotting, copying and scanning capabilities in one device.
Advantages:
Product runs in multiple computer environments
Strong compatibility position
Solid scanner controller software
Scanning path
Widecom:
The Widecom Group initially targeted wide format fax devices. Recent capital investments have helped the company launch a new line of products based on single line contact array technology at a very competitive price.
Advantages:
Aggressive price positioning leads the pack for true 400dpi scanning
Strong compatibility position with their own printers
Straight Scanning path
5.0 Conclusion
The best way to determine if a particular scanner will perform adequately for your needs is to try it. Ask your local dealer and/or service bureau to scan several of your worst drawings. This will allow you to evaluate both image quality and speed. If you plan to scan several hundred images per day, speed will be a very important factor to consider. If your documents are in poor condition, make sure that the document feed mechanism treats these documents gingerly. Other things to consider are warranty and serviceability. Find out who will fix your scanner, how long it will take, and how much it will cost.
Additional information can be obtained from the following sources:
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