HOLOGRAPHIC VERSATILE DISC
INTRODUCTION
HOLOGRAPHIC VERSATILE DISC (HVD) is an optical disc technology which would hold up to 3.9 terabytes (TB) of information. The name HVD refers to the holography technology used to read from and record to the disc. Ordinary CDs and DVDs use red laser, while blue laser allows greater density and storage capacity.
In this report we are going to tell you about the basics about the HVD. You will get to know a bit about the short history of HVD, what the blue laser is and the how and whys of the disc itself.
OVERVIEW
Holographic memory has been around for more than 40 years, but several characteristics made it difficult to implement in a consumer market. Holographic versatile disc (HVD) is a holographic storage format that looks like a DVD but is capable of storing far more data. Prototype HVD devices have been created with a capacity of 3.9 terabytes (TB) and a transfer rate of 1 gigabit per second (1 Gbps). At that capacity, an HVD could store as much information as 830 DVDs or 160 Blue-ray discs.
BASIC OF HOLOGRAPHIC MEMORY
3-D image of the Death Star created by holography
The first step in understanding holographic memory is to understand what "holographic" means. Holography is a method of recording patterns of light to produce a three-dimensional object. The recorded patterns of light are called a HOLOGRAM.
The process of creating a hologram begins with a focused beam of light -- a laser beam. This laser beam is split into two separate beams: a reference beam, which remains unchanged throughout much of the process, and an information beam, which passes through an image. When light encounters an image, its composition changes (see How Light Works to learn about this process). In a sense, once the information beam encounters an image, it carries that image in its waveforms. When these two beams intersect, it creates a pattern of light interference. If you record this pattern of light interference -- for example, in a photosensitive polymer layer of a disc -- you are essentially recording the light pattern of the image.
To retrieve the information stored in a hologram, you shine the reference beam directly onto the hologram. When it reflects off the hologram, it holds the light pattern of the image stored there. You then send this reconstruction beam to a CMOS sensor to recreate the original image.
Most of us think of holograms as storing the image of an object, like the Death Star pictured above. The holographic memory systems we're discussing here use holograms to store digital instead of analog information, but it's the same concept. Instead of the information beam encountering a pattern of light that represents the Death Star, it encounters a pattern of light and dark areas that represent ones and zeroes.
HVD TECHNOLOGY
HVD uses a technology called 'collinear holography,' in which two laser rays, one blue-green and one red, are collimated into a single beam. The role of the blue-green laser is to read the data encoded in the form of laser interference fringes from the holographic layer on the top, while the red laser serves the purpose of a reference beam and also to read the servo info from the aluminum layer - like in normal CDs - near the bottom of the disk. The servo info is meant to monitor the coordinates of the read head above the disk (this is similar to the track, head and sector information on a normal hard disk drive).
THE HOLOGRAPHIC VERSATILE DISC
Holographic memory has been around for more than 40 years, but several characteristics made it difficult to implement in a consumer market. First off, most of these systems send the reference beam and the information beam into the recording medium on different axes.
HOLOGRAPHIC VERSATILE DISC
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INTRODUCTION
HOLOGRAPHIC VERSATILE DISC (HVD) is an optical disc technology which would hold up to 3.9 terabytes (TB) of information. The name HVD refers to the holography technology used to read from and record to the disc. Ordinary CDs and DVDs use red laser, while blue laser allows greater density and storage capacity.
In this report we are going to tell you about the basics about the HVD. You will get to know a bit about the short history of HVD, what the blue laser is and the how and whys of the disc itself.
OVERVIEW
Holographic memory has been around for more than 40 years, but several characteristics made it difficult to implement in a consumer market. Holographic versatile disc (HVD) is a holographic storage format that looks like a DVD but is capable of storing far more data. Prototype HVD devices have been created with a capacity of 3.9 terabytes (TB) and a transfer rate of 1 gigabit per second (1 Gbps). At that capacity, an HVD could store as much information as 830 DVDs or 160 Blue-ray discs.
BASIC OF HOLOGRAPHIC MEMORY
3-D image of the Death Star created by holography
The first step in understanding holographic memory is to understand what "holographic" means. Holography is a method of recording patterns of light to produce a three-dimensional object. The recorded patterns of light are called a HOLOGRAM.
The process of creating a hologram begins with a focused beam of light -- a laser beam. This laser beam is split into two separate beams: a reference beam, which remains unchanged throughout much of the process, and an information beam, which passes through an image. When light encounters an image, its composition changes (see How Light Works to learn about this process). In a sense, once the information beam encounters an image, it carries that image in its waveforms. When these two beams intersect, it creates a pattern of light interference. If you record this pattern of light interference -- for example, in a photosensitive polymer layer of a disc -- you are essentially recording the light pattern of the image.
To retrieve the information stored in a hologram, you shine the reference beam directly onto the hologram. When it reflects off the hologram, it holds the light pattern of the image stored there. You then send this reconstruction beam to a CMOS sensor to recreate the original image.
Most of us think of holograms as storing the image of an object, like the Death Star pictured above. The holographic memory systems we're discussing here use holograms to store digital instead of analog information, but it's the same concept. Instead of the information beam encountering a pattern of light that represents the Death Star, it encounters a pattern of light and dark areas that represent ones and zeroes.
HVD TECHNOLOGY
HVD uses a technology called 'collinear holography,' in which two laser rays, one blue-green and one red, are collimated into a single beam. The role of the blue-green laser is to read the data encoded in the form of laser interference fringes from the holographic layer on the top, while the red laser serves the purpose of a reference beam and also to read the servo info from the aluminum layer - like in normal CDs - near the bottom of the disk. The servo info is meant to monitor the coordinates of the read head above the disk (this is similar to the track, head and sector information on a normal hard disk drive).
THE HOLOGRAPHIC VERSATILE DISC
Holographic memory has been around for more than 40 years, but several characteristics made it difficult to implement in a consumer market. First off, most of these systems send the reference beam and the information beam into the recording medium on different axes.