Hole Accumulation Diode
Encyclopedia
Hole Accumulation Diode is a patented technique of the Sony
Corporation to reduce electronic noise
in a CCD
or CMOS
imaging sensor by reducing the so-called "dark" current that occur in the absence of light falling on the imager for noise reduction and enhanced image quality.
The "hole" refers to places in a semiconductor
where an electron
has been dislodged, thus creating a positive charge. These "holes" or positive charges can be created by heat or imperfections in the creation of the imaging chip. The "holes" are accumulated, or trapped, in a separate semiconductor layer that acts as a diode
that prevents them from returning or creating noise. "HAD" technology suppresses the fixed pattern noise that results from "dark" current that occurs regardless of the amount of absorbed light. By fabricating a hole-accumulation layer below the surface of the CCD, "dark" current can be suppressed at the source.
HAD CCDs are used in consumer and professional single, as well as, three-chip video camera
s.
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
Corporation to reduce electronic noise
Electronic noise
Electronic noise is a random fluctuation in an electrical signal, a characteristic of all electronic circuits. Noise generated by electronic devices varies greatly, as it can be produced by several different effects...
in a CCD
Charge-coupled device
A charge-coupled device is a device for the movement of electrical charge, usually from within the device to an area where the charge can be manipulated, for example conversion into a digital value. This is achieved by "shifting" the signals between stages within the device one at a time...
or CMOS
CMOS
Complementary metal–oxide–semiconductor is a technology for constructing integrated circuits. CMOS technology is used in microprocessors, microcontrollers, static RAM, and other digital logic circuits...
imaging sensor by reducing the so-called "dark" current that occur in the absence of light falling on the imager for noise reduction and enhanced image quality.
The "hole" refers to places in a semiconductor
Semiconductor
A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...
where an electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
has been dislodged, thus creating a positive charge. These "holes" or positive charges can be created by heat or imperfections in the creation of the imaging chip. The "holes" are accumulated, or trapped, in a separate semiconductor layer that acts as a diode
Diode
In electronics, a diode is a type of two-terminal electronic component with a nonlinear current–voltage characteristic. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material connected to two electrical terminals...
that prevents them from returning or creating noise. "HAD" technology suppresses the fixed pattern noise that results from "dark" current that occurs regardless of the amount of absorbed light. By fabricating a hole-accumulation layer below the surface of the CCD, "dark" current can be suppressed at the source.
HAD CCDs are used in consumer and professional single, as well as, three-chip video camera
Video camera
A video camera is a camera used for electronic motion picture acquisition, initially developed by the television industry but now common in other applications as well. The earliest video cameras were those of John Logie Baird, based on the electromechanical Nipkow disk and used by the BBC in...
s.