1. HCI 530 : Seminar (HCI) Interaction

2. HCI 530: Seminar (HCI) Input Devices Mice Keyboards Scanners Joysticks Position Sensors Special Devices

3. HCI 530: Seminar (HCI) Input Devices Mice Keyboards Scanners (and Touch Screens) Joysticks Position Sensors Special Devices

4. Scanners Scanners have become an important part of the home office over the last few years. Scanner technology is everywhere and used in many ways: Flatbed scanners, also called desktop scanners, are the most versatile and commonly used scanners. In fact, these notes will focus on the technology as it relates to flatbed scanners. Sheet-fed scanners are similar to flatbed scanners except the document is moved and the scan head is immobile. A sheet-fed scanner looks a lot like a small portable printer. Handheld scanners use the same basic technology as a flatbed scanner, but rely on the user to move them instead of a motorised belt. This type of scanner typically does not provide good image quality. However, it can be useful for quickly capturing text. Drum scanners are used by the publishing industry to capture incredibly detailed images. They use a technology called a photomultiplier tube (PMT).

5. Drum Scanners Generally drum scanners are of an impressive size, and correspondingly expensive, they can cost around as much as a car or a small house. These are used by pro labs to scan your film, so it is hardly surprising that a high resolution scan can cost up to $150 a time. The drums used are typically a metre or so long, and a number of images are scanned at the same time, each negative being held on a small part of the drum's surface. The light source is in the middle of the drum, and the photocell outside. As the drum rotates, it scans every point on a circle around it. The light and photocell then move a fraction parallel to the axis of the drum for the next line to be scanned. The curved drum keeps the film to light source distance constant, and avoids problems with reflections.

6. Drum Scanners

7. The image shows: 1. A clear plastic rotatable drum 2. An original fixed to the drum 3. Light source 1 for reflective originals 4. Light source 2 for transparent originals (in drum) 5. The operators viewer 6. The lens system 7. Fine precision threaded track (mechanical, exact).

8. 8 Flat Bed Scanners The core component of the scanner is the CCD array. CCD is the most common technology for image capture in scanners. CCD is a collection of tiny light-sensitive diodes, which convert photons (light) into electrons (electrical charge). These diodes are called photosites. In a nutshell, each photosite is sensitive to light -- the brighter the light that hits a single photosite, the greater the electrical charge that will accumulate at that site.

9. Flat Bed Scanners The image of the document that you scan reaches the CCD array through a series of mirrors, filters and lenses. The exact configuration of these components will depend on the model of scanner, but the basics are pretty much the same. Firstly, the document is placed on the glass plate and the cover is closed. The inside of the cover in most scanners is flat white, although a few are black. The cover provides a uniform background that the scanner software can use as a reference point for determining the size of the document being scanned. Most flatbed scanners allow the cover to be removed for scanning a bulky object, such as a page in a thick book.

10. 10/8/2004Damian Schofield10 Flat Bed Scanners

11. 10/8/2004Damian Schofield Flat Bed Scanners

12. 10/8/2004Damian Schofield Flat Bed Scanners

13. 10/8/2004Damian Schofield Flat Bed Scanners

14. 10/8/2004Damian Schofield14 Flat Bed Scanners

15. The filter and lens arrangement vary based on the scanner. Some scanners use a three pass scanning method. Each pass uses a different color filter (red, green or blue) between the lens and CCD array. After the three passes are completed, the scanner software assembles the three filtered images into a single full-color image. Most scanners today use the single pass method. The lens splits the image into three smaller versions of the original. Each smaller version passes through a color filter (either red, green or blue) onto a discrete section of the CCD array. The scanner combines the data from the three parts of the CCD array into a single full-color image.

16. Flat Bed Scanners Scanners vary in resolution and sharpness. Most flatbed scanners have a true hardware resolution of at least 300x300 dpi. The scanner's dpi is determined by the number of sensors in a single row (x- direction sampling rate) of the CCD or CIS array by the precision of the stepper motor (y-direction sampling rate). For example, if the resolution is 300x300 dpi and the scanner is capable of scanning a letter-sized document, then the CCD has 2,550 sensors arranged in each horizontal row. A single-pass scanner would have three of these rows for a total of 7,650 sensors. The stepper motor in our example is able to move in increments equal to 1/300ths of an inch. Likewise, a scanner with a resolution of 600x300 has a CCD array with 5,100 sensors in each horizontal row.

17. Flat Bed Scanners Of course, many scanners proclaim resolutions of 4,800 x 4,800 or even 9,600x9,600. To achieve a hardware resolution with a x-direction sampling rate of 9,600 would require a CCD array of 81,600 sensors. If you look at the specifications, these high resolutions are usually labeled software-enhanced, interpolated resolution or something similar. Interpolation is a process that the scanning software uses to increase the perceived resolution of an image. It does this by creating extra pixels in between the ones actually scanned by the CCD array. These extra pixels are an average of the adjacent pixels. For example, if the hardware resolution is 300x300 and the interpolated resolution is 600x300, then the software is adding a pixel between every one scanned by a CCD sensor in each row.

18. Interaction 3D Scanners A 3D scanner is a device that analyzes a real- world object or environment to collect data on its shape and possibly its appearance (i.e. color). The collected data can then be used to construct digital, three dimensional models useful for a wide variety of applications. These devices are used extensively by the entertainment industry in the production of movies and video games. Other common applications of this technology include industrial design, orthotics and prosthetics, forensic reconstruction, reverse engineering and prototyping, quality control/inspection and documentation of cultural artifacts..

19. Interaction 3D Scanners Many different technologies can be used to build these 3D scanning devices; each technology comes with its own limitations, advantages and costs. It should be remembered that many limitations in the kind of objects that can be digitized are still present: for example optical technologies encounter many difficulties with shiny, mirroring or transparent objects.

20. Interaction 3D Scanners The purpose of a 3D scanner is usually to create a point cloud of geometric samples on the surface of the subject. These points can then be used to extrapolate the shape of the subject (a process called reconstruction). If color information is collected at each point, then the colors on the surface of the subject can also be determined.

21. Interaction 3D Scanners 3D scanners are very analogous to cameras. Like cameras, they have a cone-like field of view, and like cameras, they can only collect information about surfaces that are not obscured. While a camera collects color information about surfaces within its field of view, 3D scanners collect distance information about surfaces within its field of view. The “picture” produced by a 3D scanner describes the distance to a surface at each point in the picture.

22. Interaction 3D Scanners For most situations, a single scan will not produce a complete model of the subject. Multiple scans, even hundreds, from many different directions are usually required to obtain information about all sides of the subject. These scans have to be brought in a common reference system, a process that is usually called alignment or registration, and then merged to create a complete model. This whole process, going from the single range map to the whole model, is usually known as the 3D scanning pipeline.

23. Interaction 3D Scanners - Types Laser scanners This system uses sensors (camera’s) held within the scanning head to capture the image of the object using triangulation techniques, resulting in a point cloud (or scan data). Photogrammetry This scanner is, as its name suggests, based on standard photography practices. The system takes multiple images of the object using reference points from each differing angle from which images are taken producing scan data. Destructive Slicing Destructive slicing is another method employed regularly up until recently. CT CT Scanning or Computed Tomography has recently taken over the destructive slicing method as it is a non-destructive system ideal for small transparent parts where again, both internal and external dimensions are required. A CT scan generates three dimensional images from a large series of 2 dimensional xray images taken around a single axis of rotation. The data is reformatted as volumetric representations of structures, which could be used for either reverse engineering or inspection purposes. Trackers These measurement systems are normally used to scan large scale objects by tracking the position of the measuring device on the object and recording each time a measurement is taken. These systems can be either touch or non-contact and differing techniques are used to track the measuring device.

24. Interaction 3D Scanners - Types CT CT Scanning or Computed Tomography has recently taken over the destructive slicing method as it is a non-destructive system ideal for small transparent parts where again, both internal and external dimensions are required. A CT scan generates three dimensional images from a large series of 2 dimensional xray images taken around a single axis of rotation. The data is reformatted as volumetric representations of structures, which could be used for either reverse engineering or inspection purposes. Trackers These measurement systems are normally used to scan large scale objects by tracking the position of the measuring device on the object and recording each time a measurement is taken. These systems can be either touch or non-contact and differing techniques are used to track the measuring device.