	Optical Micrometers

Glossary

Origin of Fθ lens (Scanning method)

With an ordinary convex lens, "L" (parallel beam height), as shown below, can be expressed by the following formula:

Polygon mirror (Scanning method)

An equilateral polygonal prism which has reflecting surfaces (mirrors) is rotated to deflect a light beam orthogonally to its rotation axis. Generally, the number of reflecting surfaces ranges from six to fourteen. The more surfaces, the more target scans per rotation, allowing higher-speed scanning. However, the deflection angle decreases and the scanning width narrows.

Binarization (CCD method)

A signal output from the CCD image sensor is an analog signal. To use the signal for various measurements and differentiations, the analog signal must be first converted into a digital signal. To convert from analog to digital, a threshold (binary level) is set for the signal from the CCD image sensor, as shown below. Areas brighter than the threshold are defined as "bright", and areas darker than the threshold are defined as "dark". Thus, all areas are defined as either "bright" or "dark". This process is termed binarization, and digital signals corresponding to "bright" are defined as "1" (= HI), and those corresponding to "dark" are defined as "0" (= LO).
The intersection of the signal from the CCD image sensor and the threshold is termed "edge". Detection of this "edge" is applied for various measurements and differentiations.

Band-pass filter (CCD method)

A band-pass filter only transmits light components with a specified wavelength. The band-pass filter incorporated into the VG Series receiver has a characteristic that only passes light components with the wavelength of the semiconductor laser used in the VG.

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