Measuring instruments have evolved with the times.

The Industrial Revolution that began in Britain in the late 18th century quickly spread to many parts of the world. In the 1920s, with the spread of mass automobile production in the United States and other countries, quality control in the manufacture of parts became an important issue, and it was vital that measurements from diagrams were rendered accurately. Measurement methods using calipers, micrometers and other such instruments, as well as inspection methods using gauges,^*1 were invented to meet these requirements, and these methods are still used in manufacturing today.
Nikon has developed numerous non-contact measuring instruments based on its proprietary technologies. Examples of these include a profile projector with a wider field of view that can simultaneously measure and inspect workpieces, and a measuring microscope that can measure minute geographies. Today, these instruments are widely used in the manufacture of dies and molds essential for mass production, as well as for the measurement and inspection of manufactured parts. With today's miniaturization of high precision electronics and automobile parts, non-contact optical measurements are becoming more and more important. Demand for automated systems that can quickly and precisely measure workpieces en masse has grown in line with the expansion of automation in manufacturing.
The Computer Numerical Control (CNC) video measuring system has brought significant changes to this process. The CNC video measuring system enables automatic measurement at mass production manufacturing sites that demand consistent quality. This has led to wider use by today's manufacturers of injection-molded and stamped mechanical parts, electronics parts and other cutting-edge precision parts.

• *1A precision-machined jig used to inspect hole positions and sizes through alignment with finished parts.

The CNC video measuring system features an optical system that is suitable for high-precision two-dimensional measurements; i.e., measurements in the XY directions. With most ordinary optical systems, such as those in cameras, the closer the lens is to the subject, the larger the image is it usually produces, and vice versa. However, if focus drift occurs it causes the size of the image to change, leading to measurement errors. Nikon's NEXIV series CNC video measuring system features a telecentric optical system^*2 with which the size of the image does not change regardless of whether the image falls out of focus or how close or far the lens is. As the size of the image is constant and does not change, this optical system is ideal for image measurement and processing.

• *2An optical system in which the optical axis and principal ray are judged to be parallel on one end of a lens.

Pins rising in a grid pattern on an IC chip.

Today, maintaining the quality of manufactured products is aided by automatic measuring systems. Wherever in the world products—whether they are parts for electronics or large LCD monitors—are manufactured, they must be of identical quality. Supported by developments in software, the CNC video measuring system can automatically perceive minuscule deviations between products that were previously only possible to recognize with the human eye. For example, in the IC inspection process, the NEXIV series of CNC video measuring systems uses a pattern recognition feature to automatically detect mounted pin misalignments. After recognizing the pin position, the system takes high-precision measurements (automatic detection of image edges) by first converting video signals from its CCD into grayscale data based on levels of brightness. The system then processes these data and detects edge positions through brightness evaluation. Because the system makes judgments based on changes in brightness rather than absolute amount, it is less affected by variations in illumination and surface reflectance. This ensures high repeatability and, complemented by sub-pixel processing^*3, high resolution, thereby achieving more accurate edge detection than is possible with the human eye.

• *3This method achieves repeatability down to one-tenth the size of the original pixel by smoothing the difference of luminance between each pixel.