Image scanner

Image Scanner

Pantelegraph

T2- d161 - Fig. 74. — Récepteur du pantélégraphe Caselli

Belinograph BEP-2V - MfK Bern

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Image scanner is a device that optically scans images, printed text, handwriting, or an object, and converts it to a digital image. Commonly used in offices as well as for personal use, scanners come in a variety of forms, including flatbed, drum, and handheld. Modern scanners typically use a Charge-Coupled Device (CCD) or Contact Image Sensor (CIS) as the image sensor, unlike older models that used a photomultiplier tube as the image sensor.

Types of Scanners

There are several types of scanners, each suited for different purposes:

• Flatbed scanner: This is the most common type, resembling a small photocopier. Documents are placed on a glass window for scanning.
• Drum scanner: Used for high-resolution scanning of photographic film, these scanners use photomultiplier tubes and are known for their high quality but are much less common due to their size, cost, and complexity.
• Handheld scanner: These are small and portable, moved by hand over the surface of the image to be scanned. They are convenient but offer lower resolution.
• Sheet-fed scanner: Similar to a flatbed scanner but designed for scanning loose sheets of paper. They are commonly used in offices for scanning documents.
• Film scanner: Specifically designed for scanning film directly.

Technology

The two main types of technology used in image scanners are CCD and CIS. CCD sensors are a series of light-sensitive diodes called photosites, which convert photons into electrons (digital data). CIS sensors, on the other hand, are compact, use less power, and are cheaper to manufacture but typically offer lower quality compared to CCD sensors.

Resolution

The resolution of a scanner is measured in dots per inch (DPI). Higher DPI values indicate the ability to capture more detail in the scanned image. However, higher resolution scanning requires more storage space and processing power.

Color Depth

Color depth, also known as bit depth, is the number of bits used to indicate the color of a single pixel. Higher color depth allows a scanner to capture a wider range of colors but also results in larger file sizes.

Connectivity

Modern scanners typically connect to computers via USB or Wi-Fi, allowing for easy transfer of scanned images. Some scanners also feature memory card slots, enabling them to scan directly to a memory card.

Applications

Scanners are used in a variety of applications, including document archiving, photo reproduction, and in industries such as publishing and design. They also play a crucial role in digitizing historical texts and artwork for preservation and online access.

See Also

• Optical Character Recognition (OCR)
• Digital image processing
• Photocopier

Image scanner Resources
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