NLS-Glossary

Bessel’s method utilizes the measurement of two lens positions which produce the an image at the same image position for an object at a fixed position. In practice, this involves fixing the positions of the object and viewing screen and varying the position of the lens until two distinct lens positions are found which produce an image
at the viewing screen. 

is a term used to describe the application of a continuous (dc) voltage across, or a current through, a device that puts the device in a desirable operating condition

For example, applying a reverse dc voltage across a pin photodiode establishes the necessary electric field and puts the pin into a desirable operating condition.

Characteristic of most bar code symbologies which permits scanning of the bar code symbol in either the left-to-right or right-to-left direction. 

Able to be decoded when scanned from left to right or from right to left.                                                                                                                                                                        

A picture taken with a monochrome camera usually has 256 levels of gray. If the image just has two gray levels, it’s called “binary” image.

A binary image is a digital image that consists of only black and white pixels, with each pixel having a value of either 0 or 1. These images are also known as bilevel or two-tone images. They are commonly used in image processing and computer vision applications, as well as in digital printing and document scanning. Because they only contain two colors, they can be easily stored and manipulated using a computer.

is a transistor whose normal operation is based on the injection of minority carriers from the emitter into the base region and their diffusion to the collector where they give rise to a collector current. The voltage between the base and the emitter controls the collector current; this is the transistor action.

such as calcite are optically anisotropic which leads to an incident light beam becoming separated into ordinary (o-) and extraordinary (e-) waves with orthogonal