WO2004059628A1 - Optical device for recording and reproducing - Google Patents

Optical device for recording and reproducing Download PDF

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Publication number
WO2004059628A1
WO2004059628A1 PCT/IB2003/006157 IB0306157W WO2004059628A1 WO 2004059628 A1 WO2004059628 A1 WO 2004059628A1 IB 0306157 W IB0306157 W IB 0306157W WO 2004059628 A1 WO2004059628 A1 WO 2004059628A1
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WO
WIPO (PCT)
Prior art keywords
intensity
radiation beam
intensity distribution
modifying
central axis
Prior art date
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PCT/IB2003/006157
Other languages
French (fr)
Inventor
Johannes Schleipen
Original Assignee
Koninklijke Philips Electronics N.V.
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Publication date
Application filed by Koninklijke Philips Electronics N.V. filed Critical Koninklijke Philips Electronics N.V.
Priority to AU2003285668A priority Critical patent/AU2003285668A1/en
Publication of WO2004059628A1 publication Critical patent/WO2004059628A1/en

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Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1381—Non-lens elements for altering the properties of the beam, e.g. knife edges, slits, filters or stops
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/12—Heads, e.g. forming of the optical beam spot or modulation of the optical beam
    • G11B7/135—Means for guiding the beam from the source to the record carrier or from the record carrier to the detector
    • G11B7/1365—Separate or integrated refractive elements, e.g. wave plates
    • G11B7/1369—Active plates, e.g. liquid crystal panels or electrostrictive elements

Definitions

  • a radiation beam is used in an optical device.
  • the information carrier comprises a recording layer, whose properties can be modified locally by applying a high-intensity radiation beam.
  • the local changes induced in the recording layer correspond to written data and are subsequently used for reproducing the information by means of a lower-intensity radiation beam.
  • a phase change material is used as recording layer.
  • the recording layer is altered by the high-intensity radiation beam, but the resulting information layer is not altered during reading, because a low-intensity radiation beam is used for reading.
  • the radiation beam comprises at least a first and a second direction perpendicular to the central axis, the radiation beam having a first intensity distribution with a first mean intensity in the first direction and a second intensity distribution with a second mean intensity in the second direction, said second mean intensity being greater than the first mean intensity, wherein the means for modifying the intensity distribution are designed for reducing the second mean intensity more strongly than the first mean intensity.
  • Fig.6b shows the transmission profile of the means for modifying the intensity distribution. This transmission profile is shown for a writing mode. The grey levels of the pixels of the means for modifying the intensity distribution are higher in the second direction than in the first direction.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Optical Head (AREA)

Abstract

The invention relates to an optical device comprising a radiation source (101) for producing a radiation beam and means (103, 106) for focusing the radiation beam on an information carrier (100) along an optical path. The radiation beam has a central axis and an outer envelope, and has an intensity distribution. The optical device further comprises, in the optical path, means (104) for modifying the intensity distribution which are designed for increasing the ratio between the intensity near the envelope and the intensity near the central axis by reducing at least the intensity of the radiation beam near the central axis.

Description

Optical device for recording and reproducing
FIELD OF THE INVENTION
The present invention relates to an optical device for writing to and or reading from an information carrier.
The present invention also relates to a method for writing to and reading from an information carrier.
The present invention is particularly relevant for an optical disc apparatus for recording to and reading from an optical disc, e.g. a CD, a DVD or a Blu-Ray Disc (BD) recorder and player.
BACKGROUND OF THE INVENTION
In order to record data on and read data from an information carrier such as an optical disc, a radiation beam is used in an optical device. The information carrier comprises a recording layer, whose properties can be modified locally by applying a high-intensity radiation beam. The local changes induced in the recording layer correspond to written data and are subsequently used for reproducing the information by means of a lower-intensity radiation beam. For example, a phase change material is used as recording layer. During writing, the recording layer is altered by the high-intensity radiation beam, but the resulting information layer is not altered during reading, because a low-intensity radiation beam is used for reading.
The radiation beam is produced by a radiation source and is focused on the information layer along an optical path by means of a collimator lens and an objective lens. Along the optical path, the radiation beam is predominantly a parallel beam having a central axis and an outer envelope. The radiation beam has an intensity distribution, which depends on the radiation source and the optical device. In known optical devices, the intensity of the beam near the central axis is greater than the intensity near the outer envelope. The ratio between the intensity near the outer envelope and the intensity near the central axis of the radiation beam is called the rim intensity. In order to record data on and read data from an information layer of the information carrier, a certain amount of rim intensity is required. Actually, if the rim intensity is too low, the quality of the spot formed by the beam on the information layer is bad, and the writing and reading processes are affected. In order to increase the rim intensity, the numerical aperture of the collimator lens is reduced in the known optical devices. As a consequence, the far field of the radiation beam is cut. As this far field has a low intensity, the beam which is transmitted by the collimator lens has a relatively high rim intensity. However, cutting of the far field of the radiation beam implies that the optical throughput from the radiation source to the information carrier is reduced. The optical throughput is the ratio between the power of the radiation beam on the information carrier and the power of the radiation beam produced by the radiation source. Now, as certain intensities of the radiation beams are required for recording on and reading from the information carrier, this implies that the power of the radiation source has to be increased in order to obtain the desired beam intensities, when the numerical aperture of the collimator lens is reduced.
This is a drawback, because it decreases the lifetime of the radiation source, which is, for example, a laser diode. Moreover, this increases the electrical power consumption, which is a drawback, especially in portable devices.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an optical device comprising means for increasing the rim intensity, in which optical device the optical throughput is relatively high. To this end, the invention proposes an optical device comprising a radiation source for producing a radiation beam and means for focusing the radiation beam on an information carrier along an optical path, said radiation beam having a central axis and an outer envelope, said radiation beam having an intensity distribution, the optical device further comprising, in the optical path, means for modifying the intensity distribution which are designed for increasing the ratio between the intensity near the envelope and the intensity near the central axis by reducing at least the intensity of the radiation beam near the central axis.
According to the invention, the intensity near the central axis of the radiation beam is reduced. The intensity near the envelope of the radiation beam may also be reduced, but the means for modifying the intensity distribution are designed such that the ratio between the intensity near the envelope and the intensity near the central axis is increased. As a consequence, the rim intensity is increased. Furthermore, the far field of the radiation beam is used for writing data on and reading data from the information carrier. In this way, the optical throughput remains relatively high, at least higher than in the known optical devices where the numerical aperture of the collimator is reduced. In an advantageous embodiment, the radiation beam comprises at least a first and a second direction perpendicular to the central axis, the radiation beam having a first intensity distribution with a first mean intensity in the first direction and a second intensity distribution with a second mean intensity in the second direction, said second mean intensity being greater than the first mean intensity, wherein the means for modifying the intensity distribution are designed for reducing the second mean intensity more strongly than the first mean intensity.
The radiation sources usually used in optical devices have a beam divergence aspect ratio greater than one. This leads to an elliptically shaped spot, which affects the writing and reading of data. In the known optical devices, this is compensated by a beam shaper which reduces the intensity in a direction where the intensity is the highest. However, such a beam shaper requires careful aligning with the collimator and the objective lens, which complicates the assembling process of the optical device.
According to this advantageous embodiment, no beam shaper is required, as the means for modifying the intensity distribution are designed for compensating the beam divergence aspect ratio of the radiation source. As a consequence, the optical device is less bulky and the assembling process of the optical device is easier.
Advantageously, the means for modifying the intensity distribution are a grey scale mask. Such a grey scale mask is easy to manufacture and can be easily placed in the optical path. For example, the grey scale mask may be deposited on a glass or plastic substrate placed in the optical path. The grey scale mask may also be deposited on one of the components of the optical device, such as the collimator lens or the objective lens. In the latter case, the optical device is compact, because no other optical component is added in the optical path in order to increase the rim intensities. Preferably, the means for modifying the intensity distribution can be changed in accordance with a mode of operation of the optical device. This is particularly advantageous, because the required intensity of the radiation beam and the required rim intensity are not the same during writing and reading. Actually, a relatively low intensity of the radiation beam and a relatively high rim intensity are required during reading. During writing, an higher intensity of the radiation beam is required, but a lower rim intensity can be used. As the means for modifying the intensity distribution can be changed when the optical device goes from a writing mode to a reading mode, it is possible to take into account the required rim intensities and intensities of the radiation beam. Advantageously, the means for modifying the intensity distribution are a liquid crystal cell which can be switched between a first and a second mode, said first mode being used during writing of the information carrier in order to transmit a first percentage of the intensity of the beam near the central axis, said second mode being used during reading of the information carrier in order to transmit a second percentage of the intensity of the beam near the central axis, the second percentage being lower than the first percentage.
Such a liquid crystal cell is particularly easy to switch between the two modes, as it requires only the application of different voltages. Furthermore, such a liquid crystal cell can be easily designed so as to obtain a high rim intensity during reading and a lower rim intensity during writing, as it requires only a change in the transmission of the liquid crystal cell near the central axis of the radiation beam.
The invention also relates to a method of writing to and reading from an information carrier with an optical device comprising a radiation source for producing a radiation beam and means for focusing the radiation beam on the information carrier along an optical path, said radiation beam having a central axis and an outer envelope, said radiation beam having an intensity distribution, said method comprising a step of providing in the optical path during writing, means for modifying the intensity distribution, which means are designed for increasing the ratio between the intensity near the envelope and the intensity near the central axis by transmitting a first percentage of the intensity of the beam near the central axis, and a step of changing said means for modifying the intensity distribution during reading such that said means for modifying the intensity distribution transmit a second percentage of the intensity of the beam near the central axis, the second percentage being lower than the first percentage.
These and other aspects of the invention will be apparent from and will be elucidated with reference to the embodiments described hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in more detail by way of example with reference to the accompanying drawings, in which: - Fig. 1 shows an optical device in accordance with the invention;
- Fig. 2 shows an optical device in accordance with a first embodiment of the invention;
- Fig. 3 shows an optical device in accordance with a second embodiment of the invention; - Figs. 4a and 4c show intensity distributions of a radiation beam before and after means for modifying the intensity distribution, and Fig.4b shows a transmission profile of said means for modifying the intensity distribution, during a writing operation;
- Figs. 5a and 5c show intensity distributions of a radiation beam before and after means for modifying the intensity distribution, and Fig.5b shows a transmission profile of said means for modifying the intensity distribution, during a reading operation;
- Figs. 6a and 6c show intensity distributions of a radiation beam before and after means for modifying the intensity distribution, and Fig.6b shows a transmission profile of said means for modifying the intensity distribution, in an advantageous embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
An optical device according to the invention is depicted in Fig.l. Such an optical device comprises a radiation source 101 for producing a radiation beam 102, a collimator lens 103, means 104 for modifying the intensity distribution of the radiation beam, a beam splitter 105, an objective lens 106, a servo lens 107, detecting means 108, measuring means 109, and a controller 110. This optical device is intended for scanning an information carrier 100.
During a scanning operation, which may be a writing operation or a reading operation, the information carrier 100 is scanned by the radiation beam 102 produced by the radiation source 101. The collimator lens 103 and the objective lens 106 focus the radiation beam 102 on an information layer of the information carrier 100. The collimator lens 103 and the objective lens 106 are focusing means. During a scanning operation, a focus error signal may be detected, corresponding to an error of positioning of the radiation beam 102 on the information layer. This focus error signal may be used for correcting the axial position of the objective lens 106, so as to compensate for a focus error of the radiation beam 102. A signal is sent to the controller 110, which drives an actuator in order to move the objective lens 106 axially.
The focus error signal and the data written on the information layer are detected by the detecting means 108. The radiation beam 102, reflected by the information carrier 100, is transformed into a parallel beam by the objective lens 106, and then reaches the servo lens 107, thanks to the beam splitter 105. This reflected beam then reaches the detecting means 108. The means 104 for modifying the intensity distribution of the radiation beam are designed for transmitting only a certain percentage of the intensity of the radiation beam 102. According to the invention, the means 104 for modifying the intensity distribution transmit a relatively high percentage of the intensity of the portion of the radiation beam 102 located near the outer envelope of the radiation beam 102 and a relatively low percentage of the intensity of the portion of the radiation beam 102 located near the central axis of the radiation beam 102.
As a consequence, the rim intensity of the radiation beam 102 after the means 104 for modifying the intensity distribution is increased. Such an increase is obtained without cutting the far field of the radiation beam 102. Even if the intensity of the radiation beam 102 after the means 104 for modifying the intensity distribution is reduced, it is less strongly reduced than in the prior art, where the far field of the radiation beam is cut, especially for high rim intensities. As a consequence, given a certain rim intensity, higher optical throughput are obtained in accordance with the invention. Hence, the radiation source 101 can be operated at a lower electrical power, which decreases the power consumption of the optical device and increases the lifetime of the radiation source 101.
The means 104 for modifying the intensity distribution may be, for example, a grey scale mask, as shown in Fig.2. The means 104 for modifying the intensity distribution may alternatively be a liquid crystal cell as shown in Fig.3. The means 104 for modifying the intensity distribution have transmission profiles, as is shown in Figs. 4b and 5b.
The means 104 for modifying the intensity distribution are placed in the optical path of the radiation beam 102, which corresponds to the way travelled by the radiation beam 102 from the radiation source 101 to the information carrier 100. In this example, the means 104 for modifying the intensity distribution are placed between the collimator lens 103 and the beam splitter 105, but they may be placed elsewhere on the optical path.
Fig.2 shows an optical device in accordance with a first embodiment of the invention. In this first embodiment, the means for modifying the intensity distribution are a grey scale mask 204. In this example, the grey scale mask is deposited on the collimator lens 103. It should be noted that the grey scale mask may be deposited on another optical component of the optical device, such as the beam splitter 105 or the objective lens 106. The grey scale may might also be deposited on an additional component placed in the optical path of the radiation beam 102. If the grey scale mask is deposited on an optical component of the optical device, no additional component is needed, so that the optical device is relatively compact. The grey scale mask is, for example, a photographic filter with a transmission profile as shown in Fig. 4b or 5b.
Fig.3 shows an optical device in accordance with a second embodiment of the invention. In this second embodiment, the means for modifying the intensity distribution are a liquid crystal cell 304. This liquid crystal cell 304 has two different transmission profiles. As a consequence, the liquid crystal cell 304 can be switched between a first mode in which the liquid crystal cell 304 has a first transmission profile and a second mode in which the liquid crystal cell 304 has a second transmission profile. Depending on to the mode of operation of the optical device, i.e. writing or reading, the mode of the liquid crystal cell 304 is selected by means of voltages applied to the liquid crystal cell 304. According to this embodiment, it is possible to obtain the required rim intensities for writing and reading. Examples of modes of the liquid crystal cell 304 are given in Figs. 4b and 5b.
Such liquid crystal cells are described, for example, in "Liquid Crystal Displays", by Birendra Bahadur, Gordon & Breach Publishing Group, 1984, ISBN 0677066759.
It is important to note that alternative means for modifying the intensity distribution may be used in accordance with the invention. For example, a quantum well modulator, acousto or electro-optic modulators, or micro-electromechanics devices (MEMS) may be used.
Fig. 4a shows the intensity distribution of the radiation beam before passing through the means for modifying the intensity distribution. In this Figure, the numbers represent the intensities of the radiation beam in each portion of a section through the radiation beam. An arbitrary scale is chosen, from 0 to 100, to describe the intensities of the radiation beam. In Fig.4a, the intensities of the radiation beam relate to a radiation beam used for writing data on the information carrier 100.
In this example, the radiation beam is circularly shaped, which means that the intensity distribution is uniform in all directions starting from the central axis to the outer envelope of the radiation beam. The outer envelope is schematically represented by a circle, and the intensities of the radiation beam are schematically represented by numbers between 10 and 100. Of course, the intensity distribution of the radiation beam is continuous, although it is represented as discontinuous for convenience reasons.
The portion of the radiation beam near the central axis corresponds to the portions having an intensity equal to 100, and the portion of the radiation beam near the outer envelope corresponds to the portions having an intensity equal to 10. Of course, the portion near the central axis and the portion near the outer envelope may be defined differently. For example, the portion near the central axis may be defined as a circular area having a first radius. The portion near the outer envelope may be defined as an annular area having a second inner radius and a third outer radius. The portion near the central axis may also correspond to the portions of the radiation beam having an intensity higher than a certain percentage of the maximum intensity of the radiation beam, and the portion near the outer envelope may correspond to the rest of the radiation beam. Whatever the definition of the portion near the central axis and the portion near the outer envelope, the invention can be implemented, as soon as the portion near the outer envelope is at a greater distance from the central axis than the portion near the central axis.
In this example, with the definition of the portion near the central axis and the portion near the outer envelope given above, the rim intensity is 5 per cent of the intensity of the portion near the central axis. In order to increase this rim intensity, means for modifying the intensity distribution are used, which are described on Fig.4b.
Fig. 4b shows the transmission profile of the means for modifying the intensity distribution. These means for modifying the intensity distribution are, for example, a first grey scale mask, or a liquid crystal cell in a first mode.
In this example, the means for modifying the intensity distribution comprise pixels, each pixel having a grey level between 0 and 50, on an arbitrary scale. Hence, the transmission profile of the means for modifying the intensity distribution is discontinuous. However, it is obvious that means for modifying the intensity distribution having a continuous transmission profile may be used, without departing from the scope of the invention.
When a portion of the radiation beam is transmitted through a portion of the means for modifying the intensity distribution having a relatively high grey level, the intensity of this portion of the radiation beam is relatively strongly reduced. When a portion of the radiation beam is transmitted through a portion of the means for modifying the intensity distribution having a lower grey level, the intensity of this portion of the radiation beam is less strongly reduced. As a consequence, a grey level of the means for modifying the intensity distribution will correspond to the percentage of the intensity of the portion of the radiation beam which is not transmitted, when said portion of the radiation beam is transmitted through the portion of the means for modifying the intensity distribution having this grey level. In Fig.4b, as an arbitrary scale has been chosen for the grey levels, these grey levels also correspond to the percentages of the non-transmitted intensities. Hence, Fig.4b corresponds to an "absorption profile", from which the transmission profile can easily be deduced. This also applies to Fig. 5b and 6b.
In this example, the means for modifying the intensity distribution are designed for leaving unchanged the intensity of the portion of the radiation beam located near the outer envelope, and for reducing the intensity of the portion of the radiation beam located near the central axis. When the radiation beam having the intensity distribution of Fig.4a is transmitted through the means for modifying the intensity distribution having the transmission profile of Fig.4b, a radiation beam having the intensity distribution of Fig.4c is obtained.
The intensity of the portion near the central axis is reduced by 50 per cent after passing through the means for modifying the intensity distribution, whereas the intensity of the portion near the outer envelope is unchanged. As a consequence, the rim intensity is increased. In this example, the rim intensity beyond the means for modifying the intensity distribution is 10 per cent of the intensity of the portion near the central axis.
In this example, the mean intensity of the radiation beam beyond the means for modifying the intensity distribution is reduced by about 28 per cent, whereas the rim intensity is increased by 2. In the prior art, in order to increase the rim intensity by a factor 2, the numerical aperture of the collimator lens is reduced, and the mean intensity of the radiation beam is reduced by more than 50 percent. As a consequence, the invention renders it possible to obtain the same rim intensities as in the prior art, but with higher optical throughputs.
Fig. 5a shows the intensity distribution of the radiation beam before it passes through the means for modifying the intensity distribution, wherein the intensities of the radiation beam correspond to a radiation beam used for reading data from the information carrier 100. The scale used for the intensities of the portions of the radiation beam is the same as the scale used in Fig. 4a and 4c. For reading data, the intensity of the radiation beam is lower than for writing. In this example, the intensity is 5 times lower for reading than for writing. However, the rim intensity before the means for modifying the intensity distribution is the same as for writing, that is to say 5 per cent of the intensity near the central axis. Fig. 5b shows the transmission profile of the means for modifying the intensity distribution. These means for modifying the intensity distribution are, for example, a second grey scale mask, or a liquid crystal cell in a second mode.
When a reading operation is performed after a writing operation, the means for modifying the intensity are changed. This may be done, in the case of a grey scale mask, by physically changing the grey scale mask, that is to say by replacing the first grey scale mask with the second grey scale mask. This operation may be performed automatically inside the optical device. In the case of a liquid crystal cell, the liquid crystal cell is switched to its second mode, by means of a different voltage. This may also be performed automatically inside the optical device as a function of the mode of operation of the optical device, i.e. writing or reading.
In this example, the scale chosen for the grey levels is the same as in Fig. 4b. Compared with the transmission profile used during writing, the central portions of the means for modifying the intensity distribution have higher grey levels. This means that the percentage of the intensity of the portion near the central axis of the radiation beam, which is transmitted by these means for modifying the intensity distribution, is lower than in the case of writing.
When the radiation beam having the intensity distribution of Fig.5 a is transmitted through the means for modifying the intensity distribution having the transmission profile of Fig.5b, a radiation beam having the intensity distribution of Fig.5c is obtained.
The intensity of the portion near the central axis is reduced by 70 per cent beyond the means for modifying the intensity distribution, whereas the intensity of the portion near the outer envelope is unchanged. In this example, the rim intensity beyond the means for modifying the intensity distribution is about 17 per cent of the intensity of the portion near the central axis. Compared with the writing mode, a higher rim intensity is obtained.
The mean intensity of the radiation beam beyond the means for modifying the intensity distribution is reduced by about 35 per cent, which is higher than for writing. However, this is not a drawback, because lower intensities are used for reading than for writing.
Fig. 6a shows the intensity distribution of the radiation beam before the means for modifying the intensity distribution, for a radiation source having a divergence aspect ration greater than 1. In this example, the radiation beam comprises a first intensity distribution with a first mean intensity in a first direction and a second intensity distribution with a second mean intensity in a second direction perpendicular to the first direction. The first direction corresponds to the portions having intensities equal to 100, 40, 20 and 5, the second direction corresponds to the portions having intensities equal to 100, 50, 30 and 10. Hence, the second mean intensity is greater than the first mean intensity. This corresponds to an elliptically shaped beam, which leads to artefacts during writing and reading.
In order to remedy this drawback, the means for modifying the intensity distribution are designed for reducing the second mean intensity more strongly than the first mean intensity. Fig.6b shows the transmission profile of the means for modifying the intensity distribution. This transmission profile is shown for a writing mode. The grey levels of the pixels of the means for modifying the intensity distribution are higher in the second direction than in the first direction.
When the radiation beam having the intensity distribution of Fig.6a is transmitted through the means for modifying the intensity distribution having the transmission profile of Fig.όb, a radiation beam having the intensity distribution of Fig.6c is obtained. In Fig 6c, the intensity distributions of the radiation beam are the same in the first and second direction, which leads to a circularly shaped radiation beam. Moreover, the rim intensity is increased by the means for modifying the intensity distribution having the transmission profile of Fig.6b. Actually, the rim intensity for the radiation beam having the intensity distribution of Fig.6c is 10 per cent of the intensity of the part near the central axis, whereas the rim intensity for the radiation beam having the intensity distribution of Fig.6a is 6 per cent of the intensity of the part near the central axis.
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.

Claims

1 An optical device comprising a radiation source (101) for producing a radiation beam and means (103, 106) for focusing the radiation beam on an information carrier (100) along an optical path, said radiation beam having a central axis and an outer envelope, said radiation beam having an intensity distribution, the optical device further comprising, in the optical path, means (104) for modifying the intensity distribution which are designed for increasing the ratio between the intensity near the envelope and the intensity near the central axis by reducing at least the intensity of the radiation beam near the central axis. 2 An optical device as claimed in claim 1, wherein the radiation beam comprises at least a first and a second direction perpendicular to the central axis, the radiation beam having a first intensity distribution with a first mean intensity in the first direction and a second intensity distribution with a second mean intensity in the second direction, said second mean intensity being greater than the first mean intensity, wherein the means for modifying the intensity distribution are designed for reducing the second mean intensity more strongly than the first mean intensity.
3 An optical device as claimed in claim 1 or 2, wherein the means for modifying the intensity distribution are a grey scale mask (204).
4 An optical device as claimed in claim 1 or 2, wherein the means for modifying the intensity distribution can be changed in accordance, with a mode of operation of the optical device.
5 An optical device as claimed in claim 4, wherein the means for modifying the intensity distribution are a liquid crystal cell (304) which can be switched between a first and a second mode, said first mode being used during writing of the information carrier in order to transmit a first percentage of the intensity of the beam near the central axis, said second mode being used during reading of the information carrier in order to transmit a second percentage of the intensity of the beam near the central axis, the second percentage being lower than the first percentage.
6 A method of writing to and reading from an information carrier with an optical device comprising a radiation source for producing a radiation beam and means for focusing the radiation beam on the information carrier along an optical path, said radiation beam having a central axis and an outer envelope, said radiation beam having an intensity distribution, said method comprising the steps of : - providing in the optical path, during writing, means for modifying the intensity distribution, which means are designed for increasing the ratio between the intensity near the envelope and the intensity near the central axis by transmitting a first percentage of the intensity of the beam near the central axis; - changing said means for modifying the intensity distribution during reading, such that said means for modifying the intensity distribution transmit a second percentage of the intensity of the beam near the central axis, the second percentage being lower than the first percentage. 7 A method as claimed in claim 6, wherein the means for modifying the intensity distribution are a liquid crystal cell which can be switched between a first and a second mode, said first mode being used during writing of the information carrier in order to transmit a first percentage of the intensity of the beam near the central axis, said second mode being used during reading of the information carrier in order to transmit a second percentage of the intensity of the beam near the central axis, the second percentage being lower than the first percentage.
PCT/IB2003/006157 2002-12-30 2003-12-18 Optical device for recording and reproducing WO2004059628A1 (en)

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006024986A1 (en) 2004-09-02 2006-03-09 Arima Devices Corporation Optical device for recording and reproducing
WO2006035348A1 (en) * 2004-09-28 2006-04-06 Koninklijke Philips Electronics N.V. Optical scanning device
EP1667128A1 (en) * 2004-12-02 2006-06-07 Deutsche Thomson-Brandt Gmbh Apparatus for recording angular multiplexed pits
EP1986188A1 (en) 2007-04-27 2008-10-29 Funai Electric Co., Ltd. Optical pickup device and optical disc apparatus
EP1667129A3 (en) * 2004-12-02 2008-12-03 Thomson Licensing Apparatus for recording angular multiplexed pits

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0803869A1 (en) * 1996-03-25 1997-10-29 Lg Electronics Inc. Optical pickup apparatus for both CD and DVD
US5901131A (en) * 1995-08-04 1999-05-04 Pioneer Electronic Corporation Optical pickup used with both DVD and CD
EP1150281A2 (en) * 1995-02-02 2001-10-31 Pioneer Electronic Corporation Optical pickup apparatus and identification apparatus for identifying the type of optical record medium

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1150281A2 (en) * 1995-02-02 2001-10-31 Pioneer Electronic Corporation Optical pickup apparatus and identification apparatus for identifying the type of optical record medium
US5901131A (en) * 1995-08-04 1999-05-04 Pioneer Electronic Corporation Optical pickup used with both DVD and CD
EP0803869A1 (en) * 1996-03-25 1997-10-29 Lg Electronics Inc. Optical pickup apparatus for both CD and DVD

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2006024986A1 (en) 2004-09-02 2006-03-09 Arima Devices Corporation Optical device for recording and reproducing
WO2006035348A1 (en) * 2004-09-28 2006-04-06 Koninklijke Philips Electronics N.V. Optical scanning device
EP1667128A1 (en) * 2004-12-02 2006-06-07 Deutsche Thomson-Brandt Gmbh Apparatus for recording angular multiplexed pits
KR20060061890A (en) * 2004-12-02 2006-06-08 톰슨 라이센싱 Apparatus for recording angular multiplexed pits
EP1667129A3 (en) * 2004-12-02 2008-12-03 Thomson Licensing Apparatus for recording angular multiplexed pits
US8203925B2 (en) 2004-12-02 2012-06-19 Thomson Licsensing Apparatus for recording angular multiplexed pits
EP1986188A1 (en) 2007-04-27 2008-10-29 Funai Electric Co., Ltd. Optical pickup device and optical disc apparatus
US7894320B2 (en) 2007-04-27 2011-02-22 Funai Electric Co., Ltd. Optical pickup device and optical disc apparatus

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