What is an "in-line" video system?

An in-line video system introduces illumination into the imaging lens before the objective and aligns it with the optical axis. The "in-line" name actually refers to the type of illumination and is also known by other names such as axial, co-axial, through-the-objective, vertical, and incident brightfield. The clear difference from other types of illumination is that in this case the light is transmitted through the objective. As an example, we offer an InfiniTube In-Line Assembly that uses infinity-corrected objectives. The image from this type of objective is collimated (parallel) light prior to being focused by a secondary lens assembly onto the sensor plane. Since the light between the objective and secondary lens is collimated, the separation between the lenses can be adjusted to accept a beamsplitter that will introduce horizontally aligned input light and redirect it vertically down to the objective. This type of illumination is very efficient for high power objectives that need to evenly illuminate an opaque object, such as a semiconductor wafer. Since this type of system is very sensitive to mounting with objective powers 20X and higher, we recommend using a vibration isolation table (not available from Edmund Optics). For proper focusing, a rack and pinion movement is always suggested for the system.