The present invention relates to an optical scanning device for scanning a multi-layer information carrier.
The present invention is particularly relevant for optical data storage and optical disc apparatuses for reading and/or recording data from and/or on multi-layer optical discs.
Conventional optical scanning devices usually comprise a damper on which a disc, such as a DVD (DVD stands for Digital Versatile Disc) is fixed before scanning. The optical scanning device comprises a spinning motor in order to rotate the damper and the information carrier. The rotating information carrier is scanned by an optical beam, in order to read information written in spirally shaped tracks, or to write information in spirally shaped grooves.
European patent applications 03290470.8, 03290471.6 and 03290473.2, filed on February 2003, the 27th, are dedicated to information carriers comprising a plurality of information layers which optical properties depend on a potential difference applied between two electrodes. Such information carriers can have a relatively large number of information layers. Actually, by appropriately selecting the potential differences applied to the information layers, one information layer of the information carrier can have optical properties suitable for scanning this information layer by means of an optical beam having a wavelength, whereas the other information layers can be transparent at the wavelength of the optical beam, thus not perturbing the scanning of the scanned information layer. In these patent applications, ROM, WORM and RW information carriers are described (ROM stands for Read Only Memory, WORM for Write Once Read Many and RW for ReWritable). Hence, the expression “scanning” means either reading or writing data from or to the information carrier.
An example of such an information carrier is described in
Such an information carrier comprises a first information layer 11, a first electrolyte layer 12, a first counter electrode 13, a spacer layer 14, a second information layer 15, a second electrolyte layer 16 and a second counter electrode 17. Such an information carrier might comprise more than two information layers. For example, such an information carrier might comprise 10, 20 or up to 100 or more information layers. For example, an information carrier comprising 6 information layers is depicted in
The information layers 11 and 15 comprise pits and lands, which are obtained by means of conventional techniques, such as embossing and printing.
This information carrier is intended to be scanned by an optical beam, which has a wavelength l. The first and second electrolyte layers 12 and 16, the first and second counter electrodes 13 and 17 as well as the spacer layer 14, are chosen to be transparent at the wavelength l, or at least to have a very small absorption at this wavelength, in order not to interact with the optical beam.
In the example of
An electrochromic material is a material having optical properties, which can change as a result of electron uptake or loss. Electrochromic materials are known from those skilled in the art. For example, the publication “Electrochromism: Fundamentals and Applications”, written by Paul M. S. Monk et. al. and published in 1995, describes the properties of electrochromic materials. Preferably, the electrochromic materials used in such an information carrier are thiophene derivatives, such as poly(3,4-ethylenedioxythiophene), also called PEDT or PEDOT and described, for example, in “Poly(3,4-ethylenedioxythiophene) and Its Derivatives: Past, Present and Future”, by L. Bert Goenendaal et. al., published in Advanced Materials 2000, 12, No. 7.
In the example of
When the first information layer 11 is scanned for reading information from this first information layer 11, a potential difference V1 is applied between the first information layer 11 and the first counter electrode 13, the first information layer 11 being at a higher potential than the first counter electrode 13. A current flows from the first information layer 11 to the first counter electrode 13, whereas electrons are transported from the first counter electrode 13 to the first information layer 11. Electrons are absorbed by the electrochromic materials, which becomes reduced. For reasons of electrical neutrality, positive ions from the first electrolyte layer 12 are absorbed by the first information layer 11 or negative ions are expelled by the first information layer 11, and negative ions from the first electrolyte 12 are absorbed by the first counter electrode 13 or positive ions are expelled by the first counter electrode 13. Hence, the first counter electrode is an ion-accepting and donating electrode. The potential difference V1 is chosen so that, when applied, the absorption and reflection of the first information layer 11 becomes relatively high at the wavelength l.
Then, once the absorption and reflection of the first information layer 11 is high, information can be read from this information layer using conventional read-out techniques, such as the phase difference read-out principle used, for example, for read-out of CD-ROM, or alternatively by the reflection or absorption difference between marks and non-marks.
Once the information of the first information layer 11 has been read, the second information layer 15 is scanned. First, the first information layer 11 is made transparent by applying a potential difference −V1 between the first information layer 11 and the first counter electrode 13, which is a reverse potential difference compared to V1. As a consequence, the electrochromic material of the first information layer 11 becomes oxidized, in which state it has a low absorption and reflection at the wavelength l. Then, the second information layer 15 is made absorbent, by applying a potential difference V2 between the second information layer 15 and the second counter electrode 17. In this example, V2 is equal to V1, because the first and second information stacks comprise the same electrochromic material.
Once the absorption of the second information layer 15 is high, information can be read from this information layer. The first information layer 11 does not perturb read-out of information, because the first information layer 11 is made transparent. As a consequence, it is possible to address only one information layer, while the rest of the information carrier is transparent or has a low absorption and reflection. The desired layer is addressed by applying the suitable potential differences between the information layers and the counter electrodes of the different information stacks.
The information layers thus have optical properties, which depend on a potential difference applied between two electrodes. In the case of
As a consequence, potential differences have to be applied to such an information carrier. This is not possible with a conventional optical scanning device in which the information carrier rotates during scanning.
It is an object of the invention to provide an optical scanning device which is able to scan an information carrier comprising a plurality of information layers which optical properties depend on a potential difference applied between two electrodes.
To this end, the invention proposes an optical scanning device for scanning an information carrier comprising a plurality of information layers which optical properties depend on a potential difference applied between two electrodes, said optical scanning device comprising a fixed part comprising means for generating a signal comprising information about a selected information layer, and a rotating part comprising means for receiving said information carrier, said receiving means comprising a plurality of contacts for connecting said electrodes, means for detecting said signal, means for decoding said signal and means for applying a potential difference between the contacts connected to the electrodes corresponding to the selected information layer.
According to the invention, the information carrier is fixed to the rotating part. The rotating part comprises a plurality of contacts to which the electrodes are connected. As the rotating part and the information carrier rotate during scanning, it is not possible to apply potential differences to the information layers by means of wires connected to the fixed parts of the optical scanning device. As a consequence, the rotating part comprises the means for applying potential differences. When an information layer is selected by the optical scanning device, in order to change its optical properties, generating means are used to generate a signal comprising information about the selected information layer, which generating means are not mounted in the rotating part. A circuit in the fixed part can control the generating means in order to generate this signal. The rotating part comprises means for detecting said signal. Once the signal has been detected, it is decoded in the rotating part and the information about the selected information layer is sent to applying means, which apply a potential difference between the contacts connected to the electrodes corresponding to the selected information layer. As a consequence, no wire is used between the fixed part of the optical scanning device and the information carrier, which allows the information carrier to rotate freely.
Preferably, the means for applying a potential difference comprise a battery. This allows applying a potential difference to an information layer continuously, and thus changing its optical properties relatively rapidly.
Advantageously, the optical scanning device comprises an induction coil mounted on the rotating part and means for applying a magnetic flux through said induction coil in order to create an inductive current, the means for applying a potential difference being adapted to apply a potential difference corresponding to said inductive current between said two contacts. In this case, an induction coil mounted on the rotating part provides the energy necessary to apply potential differences. Hence, no battery is needed in the rotating part, as its rotation is converted into a current by means of the induction coil. Alternatively, a battery is used in the rotating part, and the induction coil is used in order to recharge said battery.
In a first embodiment of the invention, the generating means are a radiation source and the detecting means comprise a photosensitive detector. Preferably, the radiation source is a radiation source which is used for scanning the information carrier. In this case, the same radiation source is used in order to scan the information carrier and send information about the selected information layer. This simplifies the optical scanning device, as only one radiation source is required.
In a second embodiment of the invention, the detecting means comprise a conductive ring and the generating means comprise a brush adapted to transfer said signal to said conductive ring. According to this embodiment, an electrical contact is used in order to transfer the signal between the fixed part and the rotating part. This can be realized by means of a slip contact. Preferably, the conductive ring comprises a conductive fluid. Such a conductive fluid can easily rotate with the rotating part, while being in contact with a fixed brush or electrode.
In a third embodiment of the invention, the detecting means comprise a first conductor and the generating means comprise a second conductor adapted to transfer said signal to said first conductor by means of capacitive coupling.
In a fourth embodiment of the invention, the detecting means comprise an induction coil and the generating means comprise electromagnetic means adapted to create an inductive current inside said coil, said inductive current corresponding to said signal.
The invention also relates to a method for changing optical properties of a selected information layer in an information carrier comprising a plurality of information layers which optical properties depend on a potential difference applied between two electrodes, said method comprising the steps of generating a signal comprising information about the selected information layer, detecting and decoding said signal, and applying a potential difference between the electrodes corresponding to the selected information layer.
These and other aspects of the invention will be apparent from and will be elucidated with reference to the embodiments described hereinafter.
a and 1b show an information carrier for use with an optical scanning device in accordance with the invention;
a shows an optical scanning device in accordance with a first embodiment of the invention and
a shows a first optical scanning device in accordance with a second embodiment of the invention and
a shows a second optical scanning device in accordance with a second embodiment of the invention and
a shows an optical scanning device in accordance with a third embodiment of the invention and
A rotating part and an information carrier in accordance with the invention are depicted in
The information carrier 201 comprises a plurality of electrodes, such as electrodes 203 and 204. The information carrier 201 comprises a plurality of information layers, which optical properties depend on a potential difference applied between two electrodes. In the example of
The damper comprises contacts, such as contacts 207 and 208, which are adapted to connect the electrodes of the information carrier 201. In this example, a first electrode 203 comprises a first connection 205, which is connected to a first contact 207, and a second electrode 204 comprises a second connection 206, which is connected to a second contact 208.
The contacts of the damper 202 are connected to means for applying potential differences between two contacts, which applying means are comprised in the rotating part, as will be described in more details in the following Figures.
In the example of
An optical scanning device in accordance with the invention is depicted in
The generating means 302 are adapted to generate a signal comprising information about a selected information layer, which optical properties have to be changed. For example, an identifier of the selected information layer is encoded in this signal. Instead of an identifier of the selected information layer, the signal can comprise identifiers of the contacts between which a potential difference has to be applied. This is equivalent, as an identifier of the selected information layer can be deduced from identifiers of the contacts between which a potential difference has to be applied. The signal might comprise further information, such as an amplitude of a potential difference that has to be applied between two contacts in order to change the optical properties of the selected information layer.
This signal is, for example, a modulated signal, which is modulated as a function of the information about the selected information layer. Various types of modulation can be used, such as pulse modulation, analogue or digital frequency modulation, amplitude modulation or phase modulation.
The detecting means 303 are adapted to detect the signal generated by the generating means 302. The detected signal is provided to the addressing means 304, which are adapted to apply a potential difference between two contacts in order to change the optical properties of the information layer corresponding to the information comprised in the signal.
The addressing means 304 are depicted in details in
The signal generated by the generating means 302 is detected by the detecting means 303. The detected signal is then decoded by the decoding means 401, which then provides an identifier corresponding to the selected information layer. The decoding means 401 might provide further information, such as an amplitude of the potential difference, which has to be applied between two contacts. On the basis of this identifier, the switch controlling means 402 control the switches, so that a potential difference is applied between the contacts corresponding to the selected information layer. For example, if we assume that the selected information layer is an information layer located between the electrodes connected to contacts 311 and 312, the switch controlling means 402 switch the corresponding switches on. A potential difference is then applied between contacts 311 and 312, so that the optical properties of the corresponding information layer are changed.
The potential difference applied between two contacts is controlled by the voltage controlling means 404. Actually, in certain information carriers with a plurality of information layers which optical properties depend on a potential difference applied between two electrodes, different potential differences have to be applied, depending on the desired change of optical properties. For example, it might be necessary to apply a positive potential difference to an information layer in order to make it absorbent and reflective, and a negative potential difference in order to make it transparent.
The energy source 403 can be a battery. This battery might be rechargeable, for example by means of a photodiode illuminated by the radiation source used for scanning the information carrier, or by any other light source such as an additional LED (LED stands for Light Emitting Diode), or by means of an induction coil mounted on the rotating part, as depicted in
Alternatively, the applying means can be adapted to apply a potential difference corresponding to the detected signal between the contacts. In this case, the energy source 403 is a power converter, such as a rectifier. A part of the detected signal is decoded by the decoding means 401, another part is sent to the energy source 403, which converts this signal into power.
The energy source 403 might also be a combination of a rechargeable battery and a power converter. In this case, a part of the detected signal is converted into power, which is used for recharging the battery.
a shows an optical scanning device in accordance with a first embodiment of the invention. In this embodiment, the generating means are a radiation source 602 and the detecting means comprise a photosensitive detector 601. The radiation source 602 is, for example, a laser or a LED. The radiation source 602 generates a radiation comprising information about a selected information layer, for example a pulse modulated radiation. The photosensitive detector 601 detects this radiation and sends a signal corresponding to this radiation to the addressing means 304.
In the example of
In this embodiment, the generating means are translatable relatively to the information carrier. However, when the generating means generate the signal comprising the information about the selected information layer, they remain in a fixed position. As a consequence, the expression “fixed part” should not be understood as a part that is completely fixed, but as a part that can be fixed while the rotating part rotates, i.e. a part that does not rotate with the rotating part.
The modulated optical beam might be focussed on the photosensitive detector 601, by means of the objective lens 603, or by means of an additional lens. It is also possible to send the modulated optical beam as such to the photosensitive detector 601. In case of a pulse modulation, pulses of microseconds length can be used, as described hereinbefore. Such pulses can easily be achieved with conventional laser sources used in conventional optical scanning devices.
a shows a first optical scanning device in accordance with a second embodiment of the invention. Such an optical scanning device comprises a conductive ring 801, a brush 802 and a generator 803. The generator 803 and the brush 802 form generating means.
The generator 803 generates a signal comprising information about a selected information layer. This signal is transmitted to the brush 802, which is in electrical contact with the conductive ring 801. The signal is thus detected by the conductive ring 801, and then transmitted to the addressing means 304, which functioning has been described in
The brush 802 is for example a carbon brush. The conductive ring 801 and the carbon brush 802 form a slip contact. Such a slip contact is described, for example, in patent U.S. Pat. No. 4,398,113, granted Aug. 9, 1983. Instead of a brush, another conductive ring can be used, which is fixed relatively to the conductive ring 801, and which is in electrical contact with the conductive ring 801. In order to achieve this, a ball bearing can be used between the two conductive rings. The ball bearing is lubricated by a conductive oil or grease which may contain electrically conductive particles such as carbon particles or metal particles or a conductive polymer.
a shows a second optical scanning device in accordance with a second embodiment of the invention and
An electrode 1002 is plunged into the conductive fluid 1004, and is connected to a generator 1003, which generates a signal comprising information about a selected information layer. This signal is then transmitted through the conductive fluid to the addressing means 304, which functioning has been described in
a shows an optical scanning device in accordance with a third embodiment of the invention. In this embodiment, the optical scanning device comprises a first conductor 1101 and a second conductor 1102 connected to a generator 1103. The first conductor 1101 is mounted on the rotation axis 305 and the second conductor 1102 is a fixed part of the optical scanning device. An insulator 1104 is placed between the first and second conductor 1101 and 1102. The insulator is, for example, air or a thin film of insulating oil. The first conductor 1101, the insulator 1104 and the second conductor 1102 form a capacitive ring.
When a layer is selected, the generator 1103 generates a signal comprising information about the selected layer. This signal is applied at the poles of the second conductor 1102, which is arranged in such a way that a capacitive coupling occurs between the second conductor 1102 and the first conductor 1101. As a consequence, the signal is transmitted to the first conductor 1101, and thus detected by said first conductor 1101. The detected signal is then sent to the addressing means 304.
As capacitive coupling does not require any contact between the second conductor 1102 and the first conductor 1101, it is easily implemented in an optical scanning device according to the invention, which requires a signal transfer between a fixed part and a rotating part.
Any reference sign in the following claims should not be construed as limiting the claim. It will be obvious that the use of the verb “to comprise” and its conjugations does not exclude the presence of any other elements besides those defined in any claim. The word “a,” or “an” preceding an element does not exclude the presence of a plurality of such elements.
Number | Date | Country | Kind |
---|---|---|---|
03300026.6 | Jun 2003 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/IB04/01847 | 6/3/2004 | WO | 11/29/2005 |