Glossary - alphabet order - "H"

Half wave plate

It gives a light path difference of a half wavelength (phase difference δ = 180° + N × 360°, N is an integer ) to two linearly polarized light (parallel and perpendicular light components) when light passes through the half-waveplate. It rotates the plane of polarization by the required angle.

Half-height wavelength

An spectral property of IR cut coating or IR absorption glass, expressed by a wavelength that has transmissivity of 50 %. (See IR glass.)

Heat sink plate

It is a device made of a highly thermal-conductive material such as sapphire or quartz to release heat to the outside and transparent to incident light. The heat sink plate prevents damage or degradation of characteristics of devices caused by heat generation.

Hermetic seal

Structure diagram of crystal unit

A hermetic seal is part of a metal can package that allows a lead (pin) to protrude from the package while maintaining the vacuum condition and insulation of the output signal.


Hertz is a unit of frequency. See "Hz".

Reference: Hz , frequency

High frequency

The high frequency band is in the megahertz (MHz) section of the frequency spectrum.

Reference: Frequency band

High frequency crystal unit

A high-frequency crystal device, as typified by AT cut crystal unit, which operates in the megahertz (MHz) frequency band. However, design and fabrication of AT cut crystal units becomes difficult when the frequency reaches several hundred MHz, in which case a SAW resonator is used instead.

Reference: Frequency band

High-stability crystal oscillator

This name is used to distinguish this type of crystal oscillator from ordinary clock oscillators. Among Seiko Epson products, this indicates that the oscillator's frequency stability has a precision range better than ± 30 × 10-6. High-precision oscillators generally include a crystal oscillator that has superior temperature and ageing characteristics as well as a crystal oscillation circuit that has superior power supply voltage variation and load variation characteristics.


This is the symbol for Hertz, a unit of measure for frequency. 103 Hz = 1 kHz (kilohertz), 106 Hz = 1 MHz (megahertz), and 109 Hz = 1 GHz (gigahertz).

Page Top