A handheld text scanner is a device which can "read" printed or handwritten text, work out what it says, then turn it into a text file for a computer. This can assist in digitizing old documents which only exist in printed form. It can also be used in conjunction with a text-to-speech converter so that people with visual disabilities can "read" printed material.
One of the most important aspects of a handheld text scanner is the quality of its optical character recognition, or OCR. This is the system which converts the image captured by the scanner into text. As a simplified explanation, the system usually works by figuring out which space contains one character, then analyzes the area covering this space. The system will then break this area down into a grid of many smaller sections and designate each as simply dark or light. It will then compare the pattern across the entire area with its database and decide which character the pattern most closely matches.
The performance of a handheld text scanner can vary immensely depending on the quality and sophistication of the OCR system. Very basic systems will only work with a few, well-known fonts. The most advanced systems can even work with handwriting. In some cases it may be possible for the system to either recognize the shape of a word or to take a look at its interpretations of individual characters and figure out any mistakes it has made by looking at the context of the overall text.
The system used by any handheld text scanner will usually be less accurate than text input devices such as a digital pen system. This is because the pen system can record the direction of the individual strokes the user makes, giving it more information to evaluate individual letters. A handheld text scanner only works with text which is already in place, so has less information to work from.
The most common form of handheld text scanner is similar to a pen. This will have a lens in the position the nib would be in a normal pen. Some versions must be connected to a computer to work. Others have the processing technology built in and can store a certain amount of text on-board which can then be transferred either by a cable connection or a removable memory card. One variation on the handheld text scanner is the translation device which can scan a piece of text in a foreign language, recognize it, then produce a translated version.