WO2005001821A1

WO2005001821A1 - Optical information storage and retrieval

Info

Publication number: WO2005001821A1
Application number: PCT/ZA2004/000013
Authority: WO
Inventors: Michel Philippe Mouton; Abraham Petrus Van Wyk
Original assignee: Michel Philippe Mouton; Abraham Petrus Van Wyk
Priority date: 2003-06-27
Filing date: 2004-02-17
Publication date: 2005-01-06

Abstract

This invention provides for an information storage device that features at least one layer (14-28) containing a plurality of information storage zones (12) with the device being configured so that the electromagnetic reflection properties of the storage zones are individually alterable to one of at least four different reflective states. These states reflect one of at least two possible electromagnetic waves (38-42) having different characteristics, so as to store at least two bits of information at the storage zone. The Invention also provides a writer for storing information on the information storage device, a method of storing information on the information storage device, an information retriever for retrieving information from the information storage device, and a method of retrieving information from the information storage device.

Description

OPTICAL INFORMATION STORAGE AND RETRIEVAL

FIELD OF THE INVENTION

This invention relates, in general, to information storage and retrieval and, in particular, to an information storage device, a writer for storing information on an information storage device, a method of storing information on an information storage device, an information retriever for retrieving information from an information storage device, and a method of retrieving information from an information storage device.

BACKGROUND TO THE INVENTION

There are several different formats whereby data can be stored on an optical disc, including CD-ROM format and DVD format. The operation of these optical storage formats originates from the principle of reflection detection, where a beam of light is focused onto a surface that has been configured to contain two types of areas, each type with different reflective characteristics. One type of area focuses the incident beam of light onto an optical receiver, while the other does not. A binary value is assigned to the presence and absence of the reflected light, respectively.

By configuring the optical surface into a disc shape containing a multitude of zones that either reflect or do not reflect the incident light beam onto an optical receiver, and rotating the disc underneath a light transmitter and an optical receiver, an amount of data can be retrieved from the disc.

The current data storage formats employ a single laser to transmit a beam of light onto an optical surface. The area of an optical surface determines the amount of data that can be stored on it, as generally only one bit of information can be stored at each storage zone with the current data storage formats. This invention seeks to ameliorate the data capacity of current optical storage formats

SUMMARY OF THE INVENTION

In this specification, it is to be appreciated that an electromagnetic wave includes any electromagnetic radiation in the electromagnetic spectrum, irrespective of frequency, waveform and/or amplitude, and includes visible light, ultra violet radiation, infra red radiation, radio waves, x-rays, and/or the like. It is further to be appreciated that several electromagnetic waves may be added together to form a new and unique wave having a different frequency, waveform and/or amplitude from the separate waves from which it is formed. For example, in the visible light spectrum, different colours are formed when electromagnetic waves representing the primary colours are combined to form other electromagnetic waves. It is also to be understood that, under certain circumstances, the electromagnetic wave may be reduced into the separate waves from which it is formed, for example, white light being diffracted by a prism, and a magenta object reflecting blue light and red light. Accordingly, visible light includes colour and all variants thereof, and is to be understood to include all the primary colours and combinations thereof. Similarly, black is defined as the absence of colour and accordingly does not reflect any of the electromagnetic waves in the visible spectrum. Accordingly, this absorption of light facilitates the storing of data when interpreted in a certain manner.

According to one aspect of the invention there is provided an information storage device which includes at least one layer containing a plurality of information storage zones wherein the device is configured so that the electromagnetic reflection properties of the storage zones are individually alterable to one of at least four different reflective states which reflect or do not reflect one of at least two possible electromagnetic waves having different characteristics, so as to store at least two bits of information at the storage zone.

It is to be appreciated that the characteristics of an electromagnetic wave include frequency, waveform, and/or amplitude.

The electromagnetic reflection properties of the storage zones may be determined by the colour of the information storage zone in the visible light spectrum. The different reflective states of the storage zones may be represented by different coloured storage zones in the visible light spectrum.

The different reflective states may include a state that does not reflect any of the possible electromagnetic waves, e.g. a black state in the visible light spectrum. The different reflective states may all be capable of reflecting different electromagnetic waves. A reflective state may be able to reflect at least two different electromagnetic waves. Accordingly, a reflective state may be able to reflect a certain electromagnetic wave as well as a plurality of electromagnetic waves which combine to form that certain electromagnetic wave. For example, in the visible light spectrum, a magenta state is able to reflect the electromagnetic waves representing the colours red, blue, and magenta. One ofthe states may be capable of reflecting all of the possible electromagnetic waves, e.g. a white state in the visible light spectrum. It is to be appreciated that at least two bits of information may be stored at a storage zone by directing the possible electromagnetic waves at a zone and correlating the characteristics of the electromagnetic wave directed at the storage zone with the characteristics of the electromagnetic wave reflected from the storage zone. Accordingly, a logical value may then be assigned to the characteristics of the wave when the wave is either reflected or not, depending on the reflective state ofthe zone, enabling a zone to store at least two bits of information.

A storage zone may be configured to receive a deposit of a specific substance which substance determines the reflective state of the zone. The specific substance deposited at a storage zone may have a certain colour in the visible light spectrum to determine the reflective state of the zone in the visible light spectrum. A storage zone may be configured to receive the deposit by including a suitable cavity for receiving the substance. A storage zone may be configured to receive a deposit of the substance by being included in an alignment arrangement, for example, the zones being magnetically aligned, electrically aligned, optically aligned, and/or the like.

The information storage zone may include a thermosensitive substance, the reflective properties of which are alterable by heating the thermosensitive substance to a specific temperature. It is to be appreciated that heating the substance to a specific temperature results in the substance reflecting an electromagnetic wave with certain characteristics. The reflective properties of the thermosensitive substance may be alterable at least twice by heating the thermosensitive substance to a specific temperature, i.e. the reflective properties may be alterable several times. The alteration of the reflective properties of the thermosensitive substance may be reversible. It is to be appreciated that the substance may or may not keep the reflective properties when the substance is re-heated to a specific temperature.

The information storage zone may include a photosensitive substance, the reflective properties of which are alterable by irradiating the photosensitive substance in a specific manner, e.g. with a specific intensity, specific frequency, and/or specific duration. It is to be appreciated that irradiating the substance in a specific manner results in the substance reflecting an electromagnetic wave with certain characteristics.

The information storage zone may include an electrosensitive substance, the reflective properties of which are alterable by applying an electrical potential of a specific value and/or duration to the substance. It is to be appreciated that subjecting the substance to an electrical potential having a specific value and/or duration results in the substance reflecting an electromagnetic wave with certain characteristics. The electromagnetic reflective states of the individual information storage zones may be alterable by altering the molecular structure of the substance located at the storage zone and/or altering the surface ofthe device at the individual information storage zones, for example, through the process of spectral hole burning.

The device may be configured so that the information storage zones are located on one side of he device. The device may be configured so that the information storage zones are located on more than one side ofthe device. The information storage device may comprise a plurality of layers wherein at least four ofthe layers have differing electromagnetic reflective properties from each other, so that at least two bits of information can be stored at an information storage zone by exposing or leaving exposed one layer for reflecting, in use, one of at least two possible electromagnetic waves having different characteristics. The different reflective layers may include a layer which does not reflect the possible electromagnetic waves, e.g. a black layer in the visible light spectrum. The different reflective layers* may all be capable of reflecting different electromagnetic waves. A reflective layer may be able to reflect at least two different electromagnetic waves. Accordingly, a reflective layer may be able to reflect a certain electromagnetic wave as well as a plurality of electromagnetic waves which combine to form that certain electromagnetic wave. For example, in the visible light spectrum, a magenta layer is able to reflect the electromagnetic waves representing the colours red, blue, and magenta.

For example, in the visible light spectrum, the plurality of layers may each have a different colour from the other layers of the device. Accordingly, every colour has the intrinsic ability to reflect certain colours of visible light, each different colour having a unique wave characteristic. It is further to be appreciated that some colours are a combination of colours, and thus have the ability to reflect the colours of which it is a combination.

The different coloured layers may include at least two ofthe following coloured layers: a blue layer, a red layer, and a green layer; and at least one layer coloured a combination of any two of these primary colours.

The device may include a black layer. The device may include a white layer. For example, the different coloured layers may be selected from any one or more of the following colour combinations: blue, red, and magenta (which is a combination of blue and red); blue, green and turquoise (which is a combination of blue and green); and green, red, and yellow (which is a combination of green and red). The device typically includes a blue layer, a red layer, a green layer, a magenta layer, a turquoise layer, a yellow layer, a black layer, and a white layer. It is to be appreciated that a device with these eight layers can store three bits at a storage zone. It is to be appreciated that the amount of bits which may be stored at a storage zone is dependant on the different reflective states which the zone is able to present.

According to a second aspect of the invention, there is provided a writer for storing information on an information storage device, as described above, the writer being configured to alter, or to leave unaltered, electromagnetic reflective properties of an information storage zone of the device, so that at least two bits of information can be stored at an information storage zone by reflecting, or not reflecting, in use, one of at least two possible electromagnetic waves.

The writer may alter the electromagnetic reflective properties of an information storage zone to one of at least four different reflective states which reflect one of at least two possible electromagnetic waves having different characteristics, so as to store at least two bits of information at the storage zone. The writer may alter the electromagnetic reflection properties of an information storage zone by altering the colour ofthe zone in the visible light spectrum. The different reflective states may include a state that does not reflect any of the possible electromagnetic waves, e.g. a black state in the visible light spectrum. The different reflective states may all be capable of reflecting different electromagnetic waves. One of the states may be capable of reflecting all of the possible electromagnetic waves, e.g. a white state in the visible light spectrum. A reflective state may be able to reflect at least two different electromagnetic waves. Accordingly, a reflective state may be able to reflect a certain electromagnetic wave as well as a plurality of electromagnetic waves which combine to form that certain electromagnetic wave. For example, in the visible light spectrum, a magenta state is able to reflect the electromagnetic waves representing the colours red, blue, and magenta. The writer may alter the electromagnetic reflective properties of a storage zone by depositing a specific substance at the storage zone which substance determines the reflective properties ofthe zone. The specific substance may have a specific colour in the visible light spectrum. The writer may deposit the specific substance in a suitable cavity located at the storage zone. The writer may position the deposit of he specific substance according to an alignment arrangement. The writer may alter the reflective properties of the storage zone by heating a thermosensitive substance located at the storage zone to a specific temperature. It is to be appreciated that heating the thermosensitive substance to a specific temperature results in the thermosensitive substance reflecting an electromagnetic wave with certain characteristics. The reflective properties of the thermosensitive substance may be alterable at least twice by heating the thermosensitive substance to a specific temperature, i.e. the reflective properties may be alterable more than once. The alteration of the reflective properties of the thermosensitive substance may be reversible. It is to be appreciated that the substance may or may not keep the reflective properties when the substance is re-heated to a specific temperature.

The writer may alter the reflective properties of the storage zone by irradiating a photosensitive substance located at the storage zone in a specific manner. The intensity, frequency, and/or duration of the radiation may determine the reflective properties of the photosensitive substance. It is to be appreciated that irradiating the photosensitive substance in a specific manner results in the photosensitive substance reflecting an electromagnetic wave with certain characteristics.

The writer may alter the reflective properties of the storage zone by applying an electrical potential to an electrosensitive substance located at the storage zone. The duration and/or value of the electrical potential may determine the reflective properties of the substance. It is to be appreciated that applying an electrical potential with a certain duration and/or value to the electrosensitive substance results in the electrosensitive substance reflecting an electromagnetic wave with certain characteristics.

The writer may alter the reflective properties of the information storage zone by altering the molecular structure of a substance located at the storage zone and/or altering the surface of the device at the individual information storage zones, for example, through the process of spectral hole burning.

The writer may alter the reflective properties of the information storage zone by exposing or leaving exposed a particular layer of at least four different electromagnetically reflective layers at an information storage zone ofthe device so that at least two bits of information can be stored at each information storage zone by reflecting, or not reflecting, in use, one of at least two possible electromagnetic waves. The different reflective layers may include a layer which does not reflect the possible electromagnetic waves, e.g. a black layer in the visible light spectrum. The different reflective layers may all be capable of reflecting different electromagnetic waves. A reflective layer may be able to reflect at least two different electromagnetic waves. Accordingly, a reflective layer may be able to reflect a certain electromagnetic wave as well as a plurality of electromagnetic waves which combine to form that certain electromagnetic wave. For example, in the visible light spectrum, a magenta layer is able to reflect the electromagnetic waves representing the colours red, blue, and magenta.

The writer may expose a particular layer at an information storage zone by burning away the layers covering the layer to be exposed. The burning away of the layers may be controlled according to the depth ofthe layer to be exposed. The burning away ofthe layers may be conducted by a single laser configured to burn away a varying number of layers at each information storage zone depending on the depth of the layer to be exposed. The burning away of the layers may be conducted by a plurality of lasers, each laser configured to burn away a different predetermined number of layers so that the necessary number of layers burned away is obtained by at least one burning event of any one or any combination ofthe lasers. The writer may expose a particular layer at an information storage zone by altering the layers situated on top of the specific layer to be exposed, so that the layers situated on top of the layer to be exposed become transparent to at least one of the possible electromagnetic waves, allowing the certain electromagnetic wave to travel freely through the transparent layers. The writer may alter, or leave unaltered, the electromagnetic reflective properties of a plurality of information storage zones located on one side of the device. The writer may alter, or leave unaltered, the electromagnetic reflective properties of a plurality of information storage zones located on more than one side ofthe device. According to a third aspect of the invention there is provided a method of storing information on an information storage device, as described above, the method including the step of altering or leaving unaltered electromagnetic reflective properties of an information storage zone of the device, so that at least two bits of information can be stored at an information storage zone by reflecting, or not reflecting, in use, one of at least two possible electromagnetic waves.

The electromagnetic reflective properties of an information storage zone may be altered to one of at least four different reflective states which reflect one of at least two possible electromagnetic waves. The electromagnetic reflective properties of a storage zone may be altered by altering the colour of the zone in the visible light spectrum. The different reflective states may include a state that does not reflect any of the possible electromagnetic waves, e.g. a black state in the visible light spectrum. The different reflective states may all be capable of reflecting different electromagnetic waves. One of the states may be capable of reflecting all of the possible electromagnetic waves, e.g. a white state in the visible light spectrum. A reflective state may be able to reflect at least two different electromagnetic waves. Accordingly, a reflective state may be able to reflect a certain electromagnetic wave as well as a plurality of electromagnetic waves which combine to form that certain electromagnetic wave. For example, in the visible light spectrum, a magenta state is able to reflect the electromagnetic waves representing the colours red, blue, and magenta.

The step of altering the reflective properties of an information storage zone may include depositing a specific substance at a storage zone which substance determines the reflective properties of the storage zone. The specific substance may have a certain colour which, accordingly, determines the reflective properties of a storage zone where the substance is deposited. The specific substance may be deposited in a suitable cavity located at a storage zone. The specific substance may be deposited at a storage zone according to an alignment arrangement.

The step of altering the reflective properties ofthe storage zone may include heating a thermosensitive substance located at the storage zone to a specific temperature. It is to be appreciated that heating the thermosensitive substance to a specific temperature results in the thermosensitive substance reflecting an electromagnetic wave with certain characteristics. The reflective properties of the thermosensitive substance may be alterable at least twice by heating the thermosensitive substance to a specific temperature, i.e. the reflective properties may be alterable more than once. The alteration of the reflective properties of the thermosensitive substance may be reversible. It is to be appreciated that the substance may or may not keep the reflective properties when the substance is heated to a specific temperature.

The step of altering the reflective properties of the storage zone may include irradiating a photosensitive substance located at the storage zone in a specific manner. The intensity, frequency, and/or duration of the irradiation may determine the reflective properties of the substance.

It is to be appreciated that irradiating the photosensitive substance in a specific manner results in the photosensitive substance reflecting an electromagnetic wave with certain characteristics.

The step of altering the reflective properties of the storage zone may include applying an electrical potential to an electrosensitive substance located at the storage zone. The duration and/or value of the electrical potential may determine the reflective properties of the substance. It is to be appreciated that applying an electrical potential with a certain duration and/or value results in the electrosensitive substance reflecting an electromagnetic wave with certain characteristics. The step of altering the reflective properties of the information storage zone may include altering the molecular structure of a substance located at the storage zone and/or altering the surface of the device at the individual information storage zones, for example, through the process of spectral hole burning.

The step of altering the reflective properties of the information storage zone may include exposing or leaving exposed a particular layer of at least four different electromagnetically reflective layers at an information storage zone so that at least two bits of information can be stored at each information storage zone by reflecting or not reflecting, in use, one of at least two different electromagnetic waves.

The different reflective layers may include a layer which does not reflect the possible electromagnetic waves, e.g. a black layer in the visible light spectrum. The different reflective layers may all be capable of reflecting different electromagnetic waves. A reflective layer may be able to reflect at least two different electromagnetic waves. Accordingly, a reflective layer may be able to reflect a certain electromagnetic wave as well as a plurality of electromagnetic waves which combine to form that certain electromagnetic wave. For example, in the visible light spectrum, a magenta layer is able to reflect the electromagnetic waves representing the colours red, blue, and magenta. The step of exposing a particular layer at an information storage zone may include burning away the layers covering the layer to be exposed. The burning away of the layers may be controlled according to the depth of the layer to be exposed. The burning away of the layers may be conducted by a single laser configured to burn away a varying number of layers at each information storage zone depending on the depth of the layer to be exposed. The burning away of the layers may be conducted by a plurality of lasers, each laser configured to burn away a different predetermined number of layers so that the necessary number of layers burned away is obtained by at least one burning event of any one or any combination ofthe lasers.

The step of exposing a particular layer at an information storage zone may include altering the layers situated on top of the specific layer to be exposed, so that the layers situated on top of the layer to be exposed become transparent to at least one of the possible electromagnetic waves, allowing the certain electromagnetic wave to travel freely through the transparent layers.

The step of altering or leaving unaltered the electromagnetic reflective properties of an information storage zone may include altering or leaving unaltered the electromagnetic reflective properties of a plurality of information storage zones located on one side of the device. The step of altering or leaving unaltered the electromagnetic reflective properties of an information storage zone may include altering or leaving unaltered the electromagnetic reflective properties of a plurality of information storage zones located on more than one side ofthe device. According to a fourth aspect of the invention, there is provided an information retriever for retrieving information from an information storage device as described above, the retriever including a transmitter which transmits, in use, at least two possible electromagnetic waves to an information storage zone ofthe device in a predetermined manner; a receiver aligned, in use, with the storage device and configured to detect the presence and/or characteristics of the possible electromagnetic waves reflected by an information storage zone of the device; and a processor for generating at least two bits of information for each storage zone which bits are dependant on the correlation between the characteristics of the transmitted electromagnetic wave and the characteristics of the reflected electromagnetic wave detected or not detected by the receiver for a particular storage zone.

The transmitter may transmit a single electromagnetic wave comprised of the sum of the characteristics of a plurality of different waves to a storage zone, e.g. in the visible light spectrum where white light is comprised of three primary colours. The transmitter may individually transmit the possible electromagnetic waves with their different characteristics to a storage zone, e.g. in the visible light spectrum the transmitter may first transfer a blue light, then a green light, then a red light, and so on. Accordingly, the transmitter may include a plurality of transmitters configured to transmit a single electromagnetic wave.

For example, the transmitter may transmit a blue light, a red light, and a green light so as to retrieve information from a device including a blue zone, a red zone, a green zone, a magenta zone, a turquoise zone, a yellow zone, a black zone, and a white zone.

The transmitter may sequentially transmit all the possible electromagnetic waves to a storage zone before transmitting all the possible electromagnetic waves to the next storage zone, if the device has been configured to be read in such a manner. The transmitter may also be configured to transmit all the possible electromagnetic waves simultaneously to a storage zone before transmitting all the possible electromagnetic waves to the next storage zone, if the device has been configured to be read in such a manner. Otherwise, the transmitter may transmit one of the possible electromagnetic waves to a set of storage zones before the transmitter transmits the next possible electromagnetic wave to the same set of storage zones, if the device has been configured to be read in such a manner. The transmitter may be configured to transmit the possible electromagnetic waves to information storage zones located on one side of the information storage device. The transmitter may be configured to transmit the possible electromagnetic waves to information storage zones located on more than one side ofthe information storage device. The receiver may be configured to detect electromagnetic waves reflected from information storage zones located on one side of the information storage device. The receiver may be configured to detect electromagnetic waves reflected from information storage zones located on more than one side ofthe information storage device.

The receiver may be configured to distinguish different electromagnetic wave characteristics, e.g. amplitude, frequency and/or waveform. The receiver may be configured to detect the presence or absence of reflected electromagnetic waves. The receiver may include a plurality of receivers configured to receive a single electromagnetic wave.

The processor may be configured to generate any type of code for the reflected electromagnetic wave and/or wave characteristic of the reflected electromagnetic wave, for example, binary code, octal code, hexadecimal code, or the like. It is to be appreciated that the processor is typically configured to correlate the binary values assigned to the detected reflected electromagnetic waves when the waves are reflected from information storage zones located on more than one side of the device.

According to a fifth aspect of the invention, there is provided a method of retrieving information from an information storage device, as described above, the method including the following steps: transmitting at least two possible electromagnetic waves having different characteristics, in use, to an information storage zone ofthe device in a predetermined manner; detecting whether or not any of the possible electromagnetic waves are reflected from a storage zone; and generating at least two bits of information for each storage zone which bits are dependant on the correlation between the characteristics of the transmitted electromagnetic wave and the characteristics of the reflected electromagnetic wave detected or not detected by the receiver for a particular storage zone. The step of transmitting may include transmitting a single electromagnetic wave comprised of the sum of the characteristics of a plurality of different waves to a storage zone, e.g. in the visible light spectrum where white light is comprised of three primary colours. The step of transmitting may include individually transmitting the possible electromagnetic waves with their different characteristics to a storage zone, e.g. in the visible light spectrum the transmitter may first transfer a blue light, then a green light, then a red light, and so on. The step of transmitting may include sequentially transmitting all the possible electromagnetic waves to a storage zone before transmitting all the possible electromagnetic waves to the next storage zone, if the device has been configured to be read in such a manner. Otherwise, the step of transmitting may include transmitting one of the possible electromagnetic waves to a set of storage zones before transmitting the next possible electromagnetic wave to the same set of storage zones, if the device has been configured to be read in such a manner. The step of transmitting may also include transmitting all the possible electromagnetic waves simultaneously to a storage zone before transmitting all the possible electromagnetic waves to the next storage zone, if the device has been configured to be read in such a manner.

The step of transmitting may include transmitting the possible electromagnetic waves to information storage zones located on one side of the information storage device. The step of transmitting may include transmitting the possible electromagnetic waves to information storage zones located on more than one side ofthe information storage device.

The step of detecting may include determining the characteristics of a detected electromagnetic wave reflected by an information storage zone, such as the frequency, amplitude and/or waveform. The step of detecting may include detecting electromagnetic waves reflected from information storage zones located on one side of the mformation storage device. The step of detecting may include detecting electromagnetic waves reflected from information storage zones located on more than one side ofthe information storage device. The step of generating may include generating any type of code for the detected or not detected electromagnetic wave and/or characteristics of the reflected or not reflected electromagnetic wave, for example, binary code, octal code, hexadecimal code, or the like. The step of generating may include correlating the values assigned to the detected reflected waves when the waves are reflected from storage zones located on more than one side ofthe device.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is now described, by way of non-limiting example, with reference to the accompanying drawings wherein Figures 1, 2 and 3 show schematic diagrams representing one possible embodiment of the optical information storage device and the optical information retriever, in accordance with the invention; and Figure 4 shows a binary data chart showing binary values assigned to the different coloured layers of the optical information storage device. DETAILED DESCRIPTION OF THE DRAWINGS

In the drawings, reference numeral 12 generally refers to an optical information storage zone located on an information storage device comprised of a plurality of different layers. In this embodiment, in the visible light spectrum, 14 is a black layer, 16 is a blue layer, 18 is a red layer,

20 is a green layer, 22 is a yellow layer, 24 is a magenta layer, 26 is a turquoise layer and 28 is a white layer.

Figure 1 shows the optical information storage zone 12 comprised of the different colour layers indicated by reference numerals 14 to 28. The information retriever 30 is configured to include a transmitter 32, a receiver 34 and a processor 36 for control and management of the receiver 34 and transmitter 32.

In this embodiment of the invention, the transmitter 32 is configured to transmit three different colour light beams sequentially onto the storage zone 12. The light beams 38 to 42 represent three possible primary colours of the visible light spectrum. The light beams are represented by a green beam 38, a red beam 40 and a blue beam 42.

In Figure 1 the light beams are transmitted onto the black layer 14, where the black layer absorbs the light incident on it and no reflection takes place onto the receiver 34. The processor 36 correlates when which light is transmitted to the storage zone 12 and which, if any, light is reflected. Through this correlation, binary values can be assigned for each light. In this example, none of the three lights 38 to 42 are reflected from the black state of the information storage zone 12 to which three zero binary values are assigned, i.e. 000.

Figure 2 shows the storage zone 12 with the black layer 14, the blue layer 16, the red layer 18 and the green layer 20 removed to expose the yellow layer 22. The transmitter 32 transmits first the green light beam 38 onto the yellow layer 22. The yellow layer, the colour yellow being a combination ofthe colours green and red, reflects the green beam 38. This reflected green beam 44 is incident onto the optical receiver 34 that interprets the signal of light. In this embodiment, the processor 36 assigns a binary value of one to the reflected green beam 44, i.e. 1.

The transmitter 32 next transmits the red light beam 40 onto the yellow layer 22.

The yellow layer, the colour yellow being a combination of the colours green and red, reflects the red beam 40. This reflected red beam of light 46 is incident onto the optical receiver 34 that interprets the signal of light. In this embodiment, the processor 36 assigns a binary value of one to the reflected red beam 46, i.e. 1. The transmitter 32 now transmits the blue light beam 42 onto the yellow layer 22. The yellow layer 22, the colour yellow not being comprised of the colour blue, does not reflect the blue beam of light 42, but absorbs it. No light is thus incident onto the receiver 34. The processor 36 assigns a binary value of zero to the blue beam 42 which is not reflected, i.e. 0.

Accordingly, in the above example, the information storage zone 12 shown in Figure

2 yields three bits of information, i.e. 110.

Figure 3 shows the storage zone 12 with the black layer 14, the blue layer 16, the red layer 18, the green layer 20, the yellow layer 22, the magenta layer 24 and the turquoise layer 26 removed to expose the white layer 28. The transmitter 32 transmits first the green light beam 38 onto the white layer 28. The white layer, the colour white having the ability to reflect all the colours, reflects the green beam 38. This reflected green beam 44 is incident onto the optical receiver 34 that interprets (the signal of light. The processor 36 assigns a binary value of one to the reflected green beam 44, i.e. 1.

The transmitter 32 now transmits the red light beam 40 onto the white layer 28. The white layer, the colour white having the ability to reflect all the colours, reflects the red beam 40. This reflected red beam 46 is incident onto the optical receiver 34 that interprets the signal of light. The processor 36 assigns a binary value of one to the reflected red beam 46, i.e. 1.

The transmitter 32 now transmits the blue light beam 42 onto the white layer 28. The white layer, the colour white having the ability to reflect all the colours, reflects the blue beam 42. This reflected blue beam 48 is incident onto the optical receiver 34 that interprets the signal of light. The processor 36 assigns a binary value of one to the reflected blue beam 48, i.e. 1.

3 yields three bits of information, i.e. 111. Similarly, by altering the information storage zone 12 between the eight different reflective states 14 to 28, i.e. the different colours in this embodiment, it is possible to have eight possible binary values, e.g. 000, 001, 010, 011, 100, 101, 110, and 111.

In this embodiment of the invention the transmitter 32 transmits all the different colour light beams to a storage zone before moving to the next storage zone. It is to be appreciated that the transmitter 32 may be configured to transmit one colour light sequentially to each storage zone before the next transmitter transmits the following colour light sequentially to each storage zone.

The processor 36 is responsible for the control and management of the transmitter 32 and the receiver 34. This includes interpreting the signals received and interpreted by the receiver 34 and the generation and timing of the different colour light transmissions by the transmitter 32. The processor 36 is further responsible for the synchronisation between the transmitter 32 and the receiver 34, as well as the generation of data as interpreted by the receiver 34.

It is to be appreciated that the processor 36 may be configured to generate any type of code according to the light signals received by the receiver 34, for example, binary code, hexadecimal code, octal code, or the like. Figure 4 shows a binary data chart giving one possible configuration of binary values assigned to the different reflective states ofthe storage device. It shows the three binary values for this embodiment using three different colour light transmitters. Accordingly, each information storage zone 12 has the ability to provide three bits of information. In Figure 4, the binary values are explained as follows. 14 is a black layer, 16 is a blue layer, 18 is a red layer, 20 is a green layer, 22 is a yellow layer, 24 is a magenta layer, 26 is a turquoise layer and 28 is a white layer. The black layer 14 does not reflect the green beam 38, the red beam 40, or the blue beam 42. Accordingly, in this particular embodiment, the three bits represented by the three lights 38 to 42 are assigned the value of 000.

The three beams 38 to 42 are directed at the blue layer 16, which reflects only the blue light 42. Accordingly, the three bits are assigned the binary value of 100.

Similarly, the three beams 38 to 42 are directed at the red layer 18, which reflects only the red light 40. Accordingly, the three bits are assigned the binary value of 010.

Similarly, the three beams 38 to 42 are directed at the green layer 20, which reflects only the green light 38. Accordingly, the three bits are assigned the binary value of 001. Similarly, the three beams 38 to 42 are directed at the yellow layer 22, which reflects both the red light 40 and the green light 38. Accordingly, the three bits are assigned the binary value of 011. Similarly, the three beams 38 to 42 are directed at the magenta layer 24, which reflects both the red light 40 and the blue light 42. Accordingly, the three bits are assigned the binary value of 110. Similarly, the three beams 38 to 42 are directed at the turquoise layer 26, which reflects both the green light 38 and the blue light 42. Accordingly, the three bits are assigned the binary value of 101. Similarly, the three beams 38 to 42 are directed at the white layer 28, which reflects the green light 38, the red light 40, and the blue light 42. Accordingly, the three bits are assigned the binary value of 111.

In the manner described above, by selecting the reflective state of the information storage zones, three bits of binary data can be stored at a single information storage zone, as opposed to a single bit of binary data when compared to existing storage discs.

In another embodiment of the invention (not shown), the transmitter 32 may be configured to transmit a single white beam of light onto the information storage zone 12. Accordingly, in this embodiment, the receiver 34 is capable of interpreting the characteristics of any reflected waves, such as, for example the different colour of light reflected from the storage zone 12.

It must be appreciated that the transmitter 32 can be configured to transmit any number of different colour light beams. The transmitter 32 may be a single unit capable of transmitting different colour light beams, or the transmitter 32 may contain several individual units, each transmitting a single colour light beam.

It is also to be appreciated that in another embodiment, the optical information storage device may be comprised of a different number of coloured layers.

In another embodiment (not shown), the information storage device may be comprised, for example, of a black layer, a green layer, a blue layer and a white layer.

In this embodiment, the transmitter 32 is capable of transmitting a blue beam of light and a green beam of light. The black layer will absorb both the blue and the green light beams and no light will be reflected onto the receiver. Accordingly, the green layer will reflect only the green light beam onto the receiver and the blue layer will reflect only the blue light beam onto the receiver. The white layer will reflect both the blue and the green light beams onto the receiver. In this embodiment of the invention there are two bits of binary data stored at each storage zone, one binary bit for each different colour light transmitted by the transmitter 32. In another embodiment in the visible light spectrum, irradiating a magenta coloured storage zone with an electromagnetic wave corresponding to the colour red results in the zone reflecting the red wave, as the colour magenta is a mixture of blue and red light. The red light represents one binary data position, the value of which may be assigned dependent on whether the red light is reflected or not. In this example, a value of one is assigned if the red light is reflected. Similarly, irradiating the magenta coloured zone with an electromagnetic wave corresponding to the colour blue results in the zone reflecting the blue wave. Accordingly, the blue light represents a second binary data position, the value of which may be assigned dependent on whether the blue light is reflected or not. In this example, a value of one is assigned if the blue light is reflected. Thus the magenta coloured zone stores two one- valued bits. Accordingly, in this example, a blue zone will store one zero-valued bit where the red light is not reflected, and one one- valued bit where the blue light is reflected. A black zone will not reflect either the blue or the red light, and thus store two zero-valued bits. It is to be appreciated that a white zone will also reflect the red and the blue light, and will thus also store two one-valued bits.

It is to be appreciated that at least four reflective states are required to store two bits of data, as one bit can have two values, i.e. 0 and 1. Thus two reflective states respectively represent a zero binary value and a one binary value. The amount of data storable on the device 12 is thus dependant on the different reflective state that an information storage zone can have.

It is to be appreciated that at least two possible magnetic waves must be reflected to store two bits of data at a storage zone, i.e. 00, 01, 10, and 11. The two bits can each have either a zero value or a one value. Thus at least two different electromagnetic waves are needed to distinguish three of the four possible values, e.g. 01, 10, and 11. The last of the four possible states can be assigned to the situation where no electromagnetic waves are reflected. The value of 01 and 10 are where one of the two waves reflects, and the value of 11 is where both of the waves reflect. Another reflected electromagnetic waves may be produced as a combination of the other two waves, e.g. in the visible light spectrum where a magenta colour is produced when a blue light and a red light is combined. Accordingly, this magenta wave will then have the value of 11.

In a further example, in the visible light spectrum, an electromagnetic wave corresponding to the colour magenta irradiates a blue zone which reflects a blue light, as magenta is a mixture of blue and red. The blue zone, however, does not reflect the red light contained in the magenta. A certain value is then assigned to the reflected blue light and a certain value is assigned to the absence of reflected red light, allowing the zone to store two bits of information. The method whereby the appropriate colour layer of a storage zone is exposed may be realised through the use of a laser to burn away the layers covering the layer to be exposed. The burning away of the layers may be controlled according to the depth of the layer to be exposed. The burning away of the layers may be conducted by a single laser configured to burn away a varying number of layers at each information storage zone depending on the depth of the layer to be exposed. The burning away of the layers may be conducted by a plurality of lasers, each laser configured to burn away a different predetermined number of layers so that the necessary number of layers burned away is obtained by at least one burning event of any one or any combination ofthe lasers. It is to be appreciated that the method whereby the required colour layer of a storage zone is exposed may be through burning by laser, scratching, etching, imprinting or any similar process. It is further to be appreciated that making the layers situated on top of the required layer transparent may expose the required layer. It is to be appreciated that, in another embodiment of the invention (not shown), the information storage device comprises a single layer having a specific substance deposited at each zone on the surface of the device. This substance determines the reflective properties of the information storage zone. A storage zone may be configured to receive the deposit by including a suitable cavity for receiving the substance. A storage zone may be configured to receive a deposit ofthe substance by being included in an alignment arrangement, for example, the zones being magnetically aligned, electrically aligned, optically aligned, and/or the like.

The substance may include a thermosensitive substance, the reflective properties of which are alterable by heating the thermosensitive substance to a specific temperature. The substance may include a photosensitive substance, the reflective properties of which are alterable by irradiating the photosensitive substance in a specific manner, e.g. with a specific intensity, specific frequency, and/or specific duration. The substance may include an electrosensitive substance, the reflective properties of which are alterable by applying an electrical potential of a specific value and/or duration to the substance.

The reflective properties of an information storage zone may be alterable by altering the molecular structure of the substance located on the surface of the zone an/or the material comprising the zone itself. It is to be appreciated that alterations of the molecular structure is typically achieved by the process of spectral hole burning. The information storage device is depicted above with information storage zones on one side of the device, but it is to be appreciated that, in other embodiments, the device may have storage zones on more than one side. It is to be appreciated that the above examples are described in the visible light spectrum to facilitate the understanding of the working of the invention, but that that the invention extends to other electromagnetic waves in the electromagnetic spectrum, including ultra-violet waves, infra-red waves, x-rays, radio waves, and/or the like. It shall be understood that the examples are provided for illustrating the invention further and to assist a person skilled in the art with understanding the invention and is not meant to be construed as unduly limiting the reasonable scope ofthe invention.

The Inventors regard it as an advantage that the invention is able to increase the data storage capacity of optical information storage devices through the use of information storage zones having multiple reflective states and a transmitter transmitting multiple electromagnetic waves having different characteristics without increasing the surface area ofthe optical storage device.

Claims

1. An information storage device which includes at least one layer containing a plurality of information storage zones, wherein the device is configured so that the electromagnetic reflective properties of the storage zones are individually alterable to one of at least four different reflective states which reflect or do not reflect one of at least two possible electromagnetic waves having different characteristics, so as to store at least two bits of information at the storage zone.

2. An information storage device as claimed in claim 1, wherein the electromagnetic reflection properties ofthe storage zones are determined by the colour of the information storage zone in the visible light spectrum.

3. An information storage device as claimed in either one of claims 1 or 2, wherein the different reflective states includes a state that does not reflect any of the possible electromagnetic waves.

4. An information storage device as claimed in either one of claims 1 or 2, wherein the different reflective states are all capable of reflecting different electromagnetic waves.

5. An information storage device as claimed in any one of claims 1 to 4, wherein a reflective state is able to reflect at least two different electromagnetic waves.

6. An information storage device as claimed in claim 5, wherein the at least two different electromagnetic waves are included in a single electromagnetic wave formed by a combination of the at least two different electromagnetic waves.

7. An information storage device as claimed in any of claims 1 to 6, wherein one of the states is capable of reflecting all ofthe possible electromagnetic waves.

8. An information storage device as claimed in any one of claims 1 to 7, wherein the electromagnetic reflective states of the individual information storage zones are alterable by altering the molecular structure of the surface ofthe device at the individual information storage zones.

9. An information storage device as claimed in any one of claims 1 to 7, wherein a storage zone is configured to receive a deposit of a specific substance which substance determines the reflective state ofthe zone.

10. An information storage device as claimed in claim 9, wherein the specific substance has a certain colour in the visible light spectrum which colour determines the reflective properties of the zone in the visible light spectrum.

11. An information storage device as claimed in either one of claims 9 or 10, wherein a storage zone is configured to receive the deposit by including a suitable cavity for receiving the substance.

12. An information storage device as claimed in any one of claims 9 to 11, wherein a storage zone is configured to receive a deposit of the substance by being included in an alignment arrangement.

13. An information storage device as claimed in any one of claims 1 to 12, wherein the electromagnetic reflective states of the individual information storage zones are alterable by altering the molecular structure ofthe substance located at the storage zone.

14. An information storage device as claimed in any one of claims 1 to 12, wherein the information storage zone includes a thermosensitive substance, the reflective properties of which are alterable by heating the thermosensitive substance to a specific temperature.

15. An information storage device as claimed in claim 14, wherein the reflective properties of the thermosensitive substance are alterable at least twice by heating the substance in a specific manner.

16. An information storage device as claimed in any one of claims 1 to 12, wherein the information storage zone includes a photosensitive substance, the reflective properties of which are alterable by irradiating the photosensitive substance in a specific manner.

17. An information storage device as claimed in any one of claims 1 to 12, wherein the information storage zone includes an electrosensitive substance, the reflective properties of which are alterable by applying an electrical potential to the substance.

18. An information storage device as claimed in any one of claims 1 to 7, which comprises a plurality of layers wherein at least four of the layers have differing electromagnetic reflective properties from each other, so that at least two bits of information can be stored at an information storage zone by exposing or leaving exposed one layer for reflecting, in use, one of at least three possible electromagnetic waves having different characteristics.

19. An information storage device as claimed in any one of claims 1 to 18, which is configured so that the information storage zones are located on only one side ofthe device.

20. An information storage device as claimed in any one of claims 1 to 18, which is configured so that the information storage zones are located on more than one side ofthe device.

21. A writer for storing information on an information storage device which writer is configured to alter, or to leave unaltered, electromagnetic reflective properties of an information storage zone of the device, so that at least two bits of information can be stored at an information storage zone by reflecting or not reflecting, in use, one of at least two possible electromagnetic waves.

22. A writer as claimed in claim 21, which alters the electromagnetic reflective properties of an information storage zone to one of at least four different reflective states which reflect one of at least two possible electromagnetic waves having different characteristics, so as to store at least two bits of information at the storage zone.

23. A writer as claimed in either one of claims 21 or 22, which alters the electromagnetic reflection properties of an information storage zone by altering the colour of the zone in the visible light spectrum.

24. A writer as claimed in any one of claims 21 to 22, which alters the electromagnetic reflective properties of a storage zone by depositing a specific substance at the storage zone which substance determines the reflective properties ofthe zone.

25. A writer as claimed in claim 24, wherein the specific substance has a specific colour in the visible light spectrum which colour determines the reflective properties of the storage zone where the substance is deposited.

26. A writer as claimed in either on of claims 24 or 25, which deposits the specific substance in a suitable cavity located at the storage zone.

27. A writer as claimed in any one of claims 24 to 26, which positions the deposit of the specific substance according to an alignment arrangement.

28. A writer as claimed in any one of claims 21 to 24, which alters the reflective properties of the storage zone by heating a thermosensitive substance located at the storage zone to a specific temperature.

29. A writer as claimed in claim 28, wherein the reflective properties of the thermosensitive substance are alterable at least twice by heating the substance in a specific manner.

30. A writer as claimed in any one of claims 21 to 24, which alters the reflective properties ofthe storage zone by irradiating a photosensitive substance located at the storage zone in a specific manner.

31. A writer as claimed in any one of claims 21 to 24, which alters the reflective properties of the storage zone by applying an electrical potential to an electrosensitive substance located at the storage zone.

32. A writer as claimed in any one of claims 21 to 24, which alters the reflective properties of the information storage zone by altering the molecular structure of a substance located at the storage zone.

33. A writer as claimed in any one of claims 21 to 23, wherein the writer alters the reflective properties of the information storage zone by altering the molecular structure of the surface of the device at the individual information storage zones.

34. A writer as claimed in any one of claims 21 to 24, which alters the reflective properties ofthe information storage zone by exposing or leaving exposed a particular layer of at least four different electromagnetically reflective layers at an information storage zone ofthe device so that at least two bits of information can be stored at each information storage zone by reflecting or not reflecting, in use, one of at least two possible electromagnetic waves.

35. A writer as claimed in claim 34, which exposes a particular layer at an information storage zone by burning away the layers covering the layer to be exposed.

36. A writer as claimed in claim 35, wherein the burning away of the layers is controlled according to the depth ofthe layer to be exposed.

37. A writer as claimed in claim 36, wherein the burning away of the layers is conducted by a single laser configured to burn away a varying number of layers at each information storage zone depending on the depth ofthe layer to be exposed.

38. A writer as claimed in claim 36, wherein the burning away of the layers is conducted by a plurality of lasers, each laser configured to burn away a different predetermined number of layers so that the necessary number of layers burned away is obtained by at least one burning event of any one or any combination ofthe lasers.

39. A writer as claimed in claim 34, which exposes a particular layer at an information storage zone by altering the layers situated on top ofthe specific layer to be exposed, so that the layers situated on top of the layer to be exposed become transparent to at least one of the possible electromagnetic waves, allowing the certain electromagnetic wave to travel freely through the transparent layers.

40. A writer as claimed in any one of claims 21 to 39, which alters, or leaves unaltered, the electromagnetic reflective properties of a plurality of information storage zones located on only one side of the device.

41. A writer as claimed in any one of claims 21 to 39, which alters, or leaves unaltered, the electromagnetic reflective properties of a plurality of information storage zones located on more than one side ofthe device.

42. A method of storing information on an information storage device which includes the step of altering or leaving unaltered electromagnetic reflective properties of an information storage zone ofthe device, so that at least two bits of information can be stored at an information storage zone by reflecting or not reflecting, in use, one of at least two possible electromagnetic waves.

43. A method of storing information as claimed in claim 42, wherein the electromagnetic reflective properties of an information storage zone is altered to one of at least four different reflective states which reflect one of at least two possible electromagnetic waves.

44. A method of storing information as claimed in either one of claims 42 or 43, wherein the electromagnetic reflective properties of a storage zone is altered by altering the colour of the zone in the visible light spectrum.

45. A method of storing information as claimed in any one of claims 42 to 44, wherein the step of altering the reflective properties of an information storage zone includes depositing a specific substance at a storage zone which substance determines the reflective properties of the storage zone.

46. A method of storing information as claimed in claim 45, wherein the specific substance has a certain colour in the visible light spectrum which colour determines the reflective properties of the zone where the substance is deposited.

47. A method of storing information as claimed in either one of claims 45 or 46, wherein the specific substance is deposited in a suitable cavity located at a storage zone.

48. A method of storing information as claimed in any one of claims 45 to 47, wherein the specific substance is deposited at a storage zone according to an alignment arrangement.

49. A method of storing information as claimed in any one of claims 42 to 45 , wherein the 5 step of altering the reflective properties of the storage zone includes heating a thermosensitive substance located at the storage zone to a specific temperature.

50. A method of storing information as claimed in claim 49, wherein the reflective properties of the thermosensitive substance is alterable at least twice by heating the substance in a 0 specific manner.

51. A method of storing information as claimed in any one of claims 42 to 45, wherein the step of altering the reflective properties of the storage zone includes irradiating a photosensitive substance located at the storage zone in a specific manner.5

52. A method of storing information as claimed in any one of claims 42 to 45, wherein the step of altering the reflective properties of the storage zone includes applying an electrical potential to an electrosensitive substance located at the storage zone. 0

53. A method of storing information as claimed in any one of claims 42 to 45, wherein the step of altering the reflective properties ofthe information storage zone includes altering the molecular structure of a substance located at the storage zone.

54. A method of storing information as claimed in any one of claims 42 to 45, wherein the5 step of altering the reflective properties ofthe information storage zone includes altering the surface of the device at the individual information storage zones through the process of spectral hole burning.

55. A method of storing information as claimed in any one of claims 42 to 44, wherein the step of altering the reflective properties of the information storage zone includes exposing or leaving0 exposed a particular layer of at least four different electromagnetically reflective layers at an information storage zone so that at least two bits of information can be stored at each information storage zone by reflecting or not reflecting, in use, one of at least two different electromagnetic waves.

56. A method of storing information as claimed in claim 55, wherein the step of exposing !5 a particular layer at an information storage zone includes burning away the layers covering the layer to be exposed.

57. A method of storing information as claimed in claim 56, wherein the burning away of the layers is controlled according to the depth ofthe layer to be exposed.

58. A method of storing information as claimed in claim 57, wherein the burning away of 5 the layers is conducted by a single laser configured to burn away a varying number of layers at each information storage zone depending on the depth ofthe layer to be exposed.

59. A method of storing information as claimed in claim 57, wherein the burning away of the layers is conducted by a plurality of lasers, each laser configured to burn away a different 0 predetermined number of layers so that the necessary number of layers burned away is obtained by at least one burning event of any one or any combination ofthe lasers.

60. A method of storing information as claimed in claim 55, wherein the step of exposing a particular layer at an information storage zone includes altering the layers situated on top of the 5 specific layer to be exposed, so that the layers situated on top of the layer to be exposed become transparent to at least one of the possible electromagnetic waves, allowing the certain electromagnetic wave to travel freely through the transparent layers.

61. A method of storing information as claimed in any one of claims 42 to 60, wherein the0 step of altering or leaving unaltered the electromagnetic reflective properties of an information storage zone includes altering or leaving unaltered the electromagnetic reflective properties of a plurality of information storage zones located on only one side ofthe device.

62. A method of storing information as claimed in any one of claims 42 to 60, wherein the5 step of altering or leaving unaltered the electromagnetic reflective properties of an information storage zone includes altering or leaving unaltered the electromagnetic reflective properties of a plurality of information storage zones located on more than one side ofthe device,

63. Art information retriever for retrieving information from an information storage0 device which retriever includes a transmitter which transmits, in use, at least two possible electromagnetic waves to an information storage zone ofthe device in a predetermined manner; a receiver aligned, in use, with the storage device and configured to detect the presence and/or characteristics of the possible electromagnetic waves reflected by an information storage zone of the ι5 device; and a processor for generating at least two bits of information for each storage zone which bits are dependant on the correlation between the characteristics of the transmitted electromagnetic wave and the characteristics ofthe reflected electromagnetic wave detected or not detected by the receiver for a particular storage zone.

64. An information retriever as claimed in claim 63, wherein the transmitter transmits a single electromagnetic wave comprised of the sum of the characteristics of a plurality of different waves to a storage zone.

65. An information retriever as claimed in claim 64, wherein the transmitter includes a plurality of transmitters which are individually configured to transmit a single electromagnetic wave.

66. An information retriever as claimed in claim 63, wherein the transmitter individually transmits the possible electromagnetic waves with their different characteristics to a storage zone.

67. An information retriever as claimed in claim 63, wherein the transmitter sequentially transmits all the possible electromagnetic waves to a storage zone before transmitting all the possible electromagnetic waves to the next storage zone.

68. An information retriever as claimed in claim 63, wherein the transmitter transmits one of the possible electromagnetic waves to a set of storage zones before the transmitter transmits the next possible electromagnetic wave to the set of storage zones.

69. An information retriever as claimed in claim 63, wherein the transmitter is configured to transmit all the possible electromagnetic waves simultaneously to a storage zone before transmitting all the possible electromagnetic waves to the next storage zone.

70. An information retriever as claimed in any one of claims 63 to 69, wherein the transmitter is configured to transmit the possible electromagnetic waves to information storage zones located on only one side ofthe information storage device.

71. An information retriever as claimed in claim 63, wherein the receiver is configured to detect electromagnetic waves reflected from information storage zones located on only one side of the information storage device.

72. An information retriever as claimed in any one of claims 63 to 70, wherein the transmitter is configured to transmit the possible electromagnetic waves to information storage zones located on more than one side ofthe information storage device.

73. An information retriever as claimed in claim 71, wherein the receiver is configured to detect electromagnetic waves reflected from information storage zones located on more than one side ofthe information storage device.

74. An information retriever as claimed in any one of claims 63 to 73, wherein the receiver is configured to distinguish different electromagnetic wave characteristics.

75. An information retriever as claimed in any one of claims 63 to 74, wherein the processor is configured to generate code for the detected electromagnetic wave.

76. A method of retrieving information from an information storage device which method includes transmitting at least two possible electromagnetic waves having different characteristics, in use, to an information storage zone ofthe device in a predetermined manner; detecting whether or not any of the possible electromagnetic waves are reflected from a storage zone; and generating at least two bits of information for each storage zone which bits are dependant on the correlation between the characteristics of the transmitted electromagnetic wave and the characteristics of the reflected electromagnetic wave detected or not detected by the receiver for a particular storage zone.

77. A method of retrieving information as claimed in claim 76, wherein the step of transmitting includes transmitting a single electromagnetic wave comprised of the sum of the characteristics of a plurality of possible waves to a storage zone.

78. A method of retrieving information as claimed in claim 76, wherein the step of transmitting includes individually transmitting the possible electromagnetic waves with their different characteristics to a storage zone.

79. A method of retrieving information as claimed in claim 76, wherein the step of transmitting includes sequentially transmitting all the possible electromagnetic waves to a storage zone before transmitting all the possible electromagnetic waves to the next storage zone.

80. A method of retrieving information as claimed in claim 76, wherein the step of transmitting includes transmitting one of the possible electromagnetic waves to a set of storage zones before transmitting the next possible electromagnetic wave to the set of storage zones.

81. A method of retrieving information as claimed in claim 76, wherein the step of transmitting includes transmitting all the possible electromagnetic waves simultaneously to a storage zone before transmitting all the possible electromagnetic waves to the next storage zone.

82. A method of retrieving information as claimed in any one of claims 76 to 81, wherein the step of transmitting includes transmitting the possible electromagnetic waves to information storage zones located on only one side of the information storage device.

83. A method of retrieving information as claimed in claim 82, wherein the step of detecting includes detecting elecfromagnetic waves reflected from information storage zones located on only one side ofthe information storage device.

84. A method of retrieving information as claimed in any one of claims 76 to 81, wherein the step of transmitting includes transmitting the possible electromagnetic waves to information storage zones located on more than one side ofthe information storage device.

85. A method of retrieving information as claimed in claim 84, wherein the step of detecting includes detecting elecfromagnetic waves reflected from information storage zones located on more than one side ofthe information storage device.

86. A method of retrieving information as claimed in any one of claims 76 to 85, wherein the step of detecting includes determining the characteristics of a detected electromagnetic wave reflected by an information storage zone.

87. A method of retrieving information as claimed in any one of claims 76 to 86, wherein the step of generating includes generating code for the detected electromagnetic wave.

88. A method of retrieving information as claimed in any one of claims 76 to 86, wherein the step of generating includes generating code for not detecting a reflected electromagnetic wave.