U.S. patent application number 12/602431 was filed with the patent office on 2010-11-04 for laser reactive media and apparatus and method for writing an image onto such media.
Invention is credited to Anthony Miles, Robert Glyn Miles.
Application Number | 20100277561 12/602431 |
Document ID | / |
Family ID | 38265471 |
Filed Date | 2010-11-04 |
United States Patent
Application |
20100277561 |
Kind Code |
A1 |
Miles; Anthony ; et
al. |
November 4, 2010 |
LASER REACTIVE MEDIA AND APPARATUS AND METHOD FOR WRITING AN IMAGE
ONTO SUCH MEDIA
Abstract
An optical disk label writing method for writing a label on an
optical disc uses a similar writing operation to that used to write
data to the disc. The disc has a label side including a laser
reactive material for forming the label image, and a tracking
format that can be tracked by a writing laser in a similar way to a
writing operation. A computer program is provided for converting a
label image to a disk image file for writing to the label side.
Inventors: |
Miles; Anthony; (Bridgend,
GB) ; Miles; Robert Glyn; (Bridgend, GB) |
Correspondence
Address: |
GARRETT IP, LLC;C/O CPA Global
P.O. BOX 52050
MINNEAPOLIS
MN
55402
US
|
Family ID: |
38265471 |
Appl. No.: |
12/602431 |
Filed: |
May 29, 2008 |
PCT Filed: |
May 29, 2008 |
PCT NO: |
PCT/GB08/01814 |
371 Date: |
June 24, 2010 |
Current U.S.
Class: |
347/253 |
Current CPC
Class: |
B41J 2/455 20130101;
G11B 7/0938 20130101; G11B 23/40 20130101; G11B 7/00736 20130101;
G11B 7/0037 20130101; B41J 2/442 20130101; G11B 7/24094 20130101;
B41J 2/525 20130101; G11B 7/24 20130101 |
Class at
Publication: |
347/253 |
International
Class: |
B41J 2/47 20060101
B41J002/47 |
Foreign Application Data
Date |
Code |
Application Number |
May 29, 2007 |
GB |
0710196.7 |
Nov 16, 2007 |
GB |
0722588.1 |
Claims
1. An apparatus for writing an image to a laser reactive image
medium, wherein the reaction of said laser reactive image medium is
dependent on a frequency of laser light received, the apparatus
being arranged to apply to said medium a laser beam having a
selected one of a plurality of discrete frequencies, and to
generate at least one of said plurality of discrete frequencies by
heterodyning two others of said discrete frequencies.
2. (canceled)
3. The apparatus of claim 1, further comprising: a first laser,
operable to output a first laser beam having a first frequency; a
second laser, operable to output a second laser beam having a
second frequency different to the first frequency; means to direct
the respective output beams of the first and second lasers at a
coincident position; so as to generate a third frequency
corresponding to the sum of the first and second frequencies, and a
fourth frequency corresponding to the difference between the first
and second frequencies; and means for selectively applying one or
more of said first to fourth frequencies to said medium.
4. The apparatus of claim 3, wherein said means to direct the
respective output beams of the first and second lasers at a
coincident position comprises a first means operable to focus the
output beam of the first laser at a first position and second means
operable to focus the output beam of the second laser at a
coincident position to the first position.
5. The apparatus of claim 1, further comprising means for
monitoring the reaction of the laser reactive image medium being
illuminated by the laser light.
6. The apparatus of claim 5, wherein the first and/or second laser
is operable to be deactivated in response to the reaction
monitoring means detecting a predetermined reaction.
7. The apparatus of claim 1, wherein the reaction of the laser
reactive image medium is a colour change reaction.
8. The apparatus of claim 1, further comprising: means arranged to
receive one or more data files incorporating the image, wherein
said apparatus is responsive to said one or more data files to
write said image to said laser reactive image medium.
9. The apparatus of claim 1, wherein said laser reactive image
medium comprises an optical disc.
10. A laser reactive image medium comprising laser reactive
material able to change colour in reaction to being illuminated
with laser light, and wherein the colour change so effected is
dependent on the frequency of laser light illuminating the laser
reactive material, wherein the laser reactive material is able to
react by changing to: a first colour if illuminated by laser light
of a first frequency; a second colour if illuminated by laser light
of a second frequency; and a third colour if illuminated by laser
light having a frequency corresponding to the sum of the first and
second frequencies.
11. (canceled)
12. (canceled)
13. The laser reactive image medium of claim 10, wherein the laser
reactive material is able to react by changing to: a fourth colour
if illuminated by laser light having a frequency corresponding to
difference between the first and second frequencies.
14. The laser reactive image medium of claim 10, wherein said laser
reactive image medium comprises an optical disc.
15. The optical disc of claim 14, comprising a label side on which
a visible image is writable by a laser of an optical disc drive,
the label side having a format recognisable as a data writable side
by the optical disc drive, wherein the label side comprises a layer
of said laser reactive material.
16. The apparatus of claim 15, wherein the label side includes a
track for tracking by data writing means.
17. A method of writing an image to a laser reactive image medium,
wherein the reaction of said medium is dependent on a frequency of
laser light received, comprising: applying to said medium a laser
beam having a selected one of a plurality of discrete frequencies;
and generating at least one of said plurality of discrete
frequencies by heterodyning two others of said discrete
frequencies.
18. (canceled)
19. The method of claim 17, further comprising: directing the
respective output beams of a first laser, having a first frequency,
and a second laser, having a second frequency, at a coincident
position: so as to generate a third frequency corresponding to the
sum of the first and second frequencies and a fourth frequency
corresponding to the difference between the first and second
frequencies; and selectively applying one or more of said first to
fourth frequencies to said medium.
20. The method of claim 17, further comprising: monitoring the
reaction of a portion of the laser reactive image medium
illuminated by the applied laser light.
21. The method of claim 20, further comprising: de-energising the
first laser and/or the second laser when a predetermined reaction
is detected.
22. The method of claim 17, wherein said laser reactive medium
reacts to the applied laser light by changing to a different
colour, where the colour change effected is dependent on the
frequency of the applied laser light.
23. The method of claim 17, further comprising: receiving one or
more data files incorporating the image, and writing the image to
said laser reactive image medium in response to said receiving said
one or more data files.
24. An apparatus for writing an image to a laser reactive image
medium, comprising: a laser generating device operable to
selectively illuminate and vaporise at least one portion of said
laser reactive image medium with a laser beam.
25. The apparatus of claim 24, further comprising: means arranged
to receive one or more data files incorporating the image; wherein
said apparatus is responsive to said one or more data files to
write said image to said laser reactive image medium.
26. The apparatus of claim 24, further comprising: means for
monitoring a reaction of the at least one portion of the laser
reactive image medium.
27. The apparatus of claim 26, wherein the laser generating device
is operable to be activated in response to said reaction monitoring
means detecting a first predetermined reaction and deactivated in
response to the reaction monitoring means detecting a second
predetermined reaction.
28. The apparatus of claim 27, wherein said reaction of the at
least one portion of the laser reactive image medium is a colour
change reaction.
29. The apparatus of claim 24, wherein said laser reactive image
medium comprises an optical disc.
30-72. (canceled)
73. An optical drive for writing a label to an optical disc,
comprising: first writing means operable to write a visible image
to said optical disc; and a second writing means operable to write
data to said optical disc; wherein said first writing means
comprises a print head operable to emit simultaneously at least two
beams of laser light.
74. The optical drive of claim 73 wherein said print head comprises
an array of laser generating devices operable to emit
simultaneously said at least two beams of laser light.
75. The optical drive of claim 73 wherein said print head comprises
a single laser generating device coupled to two or more optical
fibres, wherein the ends of the two or more optical fibres that are
not attached to said laser generating device are arranged to form
an array and to emit simultaneously said at least two beams of
laser light.
76. The optical drive of claim 73, wherein the second writing means
is controllable so as to vary the frequency and/or intensity of
said at least two beams of laser light.
77-82. (canceled)
83. A laser reactive image medium comprising a continuous layer of
a laser reactive material able to change colour in reaction to
being illuminated with laser light, and wherein the colour change
so effected is dependent on the frequency of laser light
illuminating the laser reactive material.
84. The laser reactive image medium of claim 83, wherein the laser
reactive material is able to react by changing to: a first colour
if illuminated by laser light of a first frequency; and a second
colour if illuminated by laser light of a second frequency.
85. The laser reactive image medium of claim 84, wherein the laser
reactive material is able to react by changing to: a third colour
if illuminated by laser light having a frequency corresponding to
the sum of the first and second frequencies.
86. The laser reactive image medium of claim 84, wherein the laser
reactive material is able to react by changing to: a fourth colour
if illuminated by laser light having a frequency corresponding to
the difference between the first and second frequencies.
Description
[0001] The present invention relates to laser reactive media,
particularly to optical discs with writable labels, and means for
printing on such media.
BACKGROUND TO THE INVENTION
[0002] Writable optical discs are widely used for the storage of
data, such as audio, video or photographic images. Many users have
a large collection of such data on multiple optical discs, and need
to identify the content of each disc. This can be done by marking
the non-writable side of a single sided disc with a marker pen, but
this can damage the disc and may not provide a very clear or
attractive label.
[0003] Another approach is to print a label of the same shape and
size as the optical disc using a separate printer, and to affix the
printed label to the optical disc. Printable label media may be
used for this purpose, together with software for designing the
label. However, the label may become detached from the disc, or may
become partially detached and jam an optical disc drive.
[0004] U.S. Pat. No. 6,074,031 describes an optical disk drive
including an inkjet print head, so that the drive can print a label
on a disk as well as read or write data to or from the disc.
However, this would lead to a very complex and expensive drive that
would be prone to failure.
[0005] U.S. Pat. No. 6,771,297 describes a system for writing an
optical disc label using a laser, possibly the same laser that is
used to write data to the optical disc, and a thermally sensitive
layer on the label side of the disc. A similar system is currently
available on the market under the Hewlett-Packard Lightscribe.TM.
brand. The Lightscribe.TM. system requires a Lightscribe-enabled
optical drive, and it is not possible to write labels on
Lightscribe discs with non-Lightscribe-enabled drives. Furthermore,
the Lightscribe system is only able to write labels in monochrome;
a colour version is disclosed in U.S. Pat. No. 6,771,297, but is
not available on the market. Most importantly, the Lightscribe
system requires 20 to 40 minutes to write the label, which is
considerably longer than the time taken to write data to the
disc.
STATEMENT OF THE INVENTION
[0006] According to one aspect of the present invention, there is
provided an optical disc label writing method for writing a label
on an optical disc using a similar writing operation to that used
to write data to the disc. The disc has a label writing side
including a laser reactive material for forming the label image,
and a tracking format that can be tracked by a writing laser in a
similar way to a writing operation. Hence, according to another
aspect of the invention, there is provided an optical disc having a
laser-reactive label writing side carrying a tracking format.
[0007] Since the label writing side appears to the optical disc
drive as a standard data-writable disc, a label may be written on
the disc using a standard optical disc writing drive. However,
software is required to convert a label image to a data file
suitable for writing to the optical disc. Hence, according to
another aspect of the invention there is provided a computer
program arranged to convert an image for an optical disc label into
one or more data files suitable for writing to an optical disc.
[0008] The label side may not be capable of storing the data that
the optical drive attempts to write in a data writing operation;
however, as far as the optical drive is concerned, the writing
operation may be substantially the same as a data writing
operation. However, a visible label image is written instead of
data readable by the optical drive.
[0009] According to a further aspect of the present invention,
there is provided an optical disk label writing apparatus and
method for writing a label on an optical disc using a writing
operation different and separate to that used to write data to the
disc. The disc has a label writing side including a laser reactive
material for forming the label image, and a laser writing print
head emitting at least two laser beams from an array is used to
write an image on the label writing side of the disc.
[0010] According to a further aspect of the present invention,
there is provided an apparatus and method for writing an image to a
laser reactive medium where the laser reactive material exhibits
different reactions depending on the frequency of laser light
received. A laser writing head is arranged to heterodyne the
outputs of at least two laser generating devices to generate a
range of discrete frequencies of laser light. The laser writing
head is operable to supply to the laser reactive material a
selected one or more frequencies of laser light from the range of
discrete frequencies of laser light produced by heterodyning.
[0011] According to a further aspect of the present invention,
there is provided an apparatus and method for writing an image to a
laser reactive medium, where the laser reactive medium has one or
more laser reactive layers, each layer having a different colour.
The laser reactive medium is able to vaporise when illuminated by a
laser beam. A laser writing head is operable to emit a laser beam
to vaporise portions of the laser reactive material. A colour
recognising sensor may be provided to monitor the colour of the
laser reactive medium and de-energise the laser beam when a desired
colour is obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Embodiments of the invention will now be described with
reference to the drawings identified below:
[0013] FIG. 1 shows the construction of an optical disc in an
embodiment of the invention;
[0014] FIG. 2 is a flowchart of a method of writing a label in an
embodiment of the invention;
[0015] FIG. 3 shows a diagrammatic view of a laser writing print
head according to a second embodiment of the invention;
[0016] FIG. 4 shows a plan view of the laser writing print head of
FIG. 3;
[0017] FIG. 5 shows a diagrammatic view of a laser writing head
according to a third embodiment of the invention;
[0018] FIG. 6 shows the construction of an optical disc in a fourth
embodiment of the invention; and
[0019] FIG. 7 shows a diagrammatic view of a laser writing head
according to the fourth embodiment of the invention.
DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION
First Embodiment
[0020] As shown in FIG. 1, an optical disc 1 in a first embodiment
of the invention has a data side 2 and a label side 3. The data
side 2 is arranged to store data written thereto by an optical disc
drive; it comprises, in order from the outer surface of the optical
disc 1 inwards: a substrate 2a carrying a spiral track; a data
writing layer 2b that stores data written thereto; and a reflective
layer 2c for reflecting the laser of the optical disc drive so as
to enhance its effect on the data writing layer 2b. The label side
3 is arranged to carry a visible pattern written thereto by the
optical disc drive; it comprises in order from the outer surface of
the optical disc 1 inwards: a substrate 3a carrying a spiral track;
a label writing layer 3b; and a reflective layer 3c for reflecting
the laser of the optical disc drive so as to enhance its effect on
the label writing layer 2b.
[0021] During construction of the disc 1, the different layers 2a
to 2c and 3a to 3c are integrated to form the optical disc 1.
[0022] The label writing layer 3b comprises an array of pixels P,
each comprising a pattern of dots of different writing colours: in
this case red, green, blue and black. Each dot comprises a material
that reacts to the laser of the optical disc drive by changing from
a base colour (e.g. white or colourless) to the writing colour.
Preferably, this colour change is irreversible or permanent. The
pixels P are distributed substantially evenly over the writable
surface of the label writing layer 3b. The pixels P may be
deposited by printing onto the inner side of the substrate 3a, or
by another forming or depositing method.
[0023] The dots may be formed from one or more laser-writable inks,
for example as disclosed in WO-A-05/068207. Any suitable laser
reactive material may be used to form the dots, examples include:
[0024] Cyanine, which is a non-systematic name of a synthetic dye
family with the common molecular formula:
[0024] ArN+.dbd.CH[CH.dbd.CH]n.dbd.NAr [0025] where two quaternized
nitrogens are joined by a poly-methane chain. Both nitrogens are
each independently part of a heteroaromatic moiety, such as
imidazole, pyridine, pyrrole, quinoline, thiazole, etc. [0026]
Leuco dyes [0027] Thermochromic dyes are based on mixtures of Leuco
dyes with suitable other chemicals, displaying a color change
(usually between the colourless Leuco form and the coloured form)
independent of temperature. The dyes are rarely applied on
materials directly; they are usually in the form of microcapsules
with the mixture sealed inside. An illustrative example is where
microcapsules with crystal violet lactone, weak acid, and a
dissociable salt dissolved in dodecanol are applied to a substrate;
when the solvent is solid, the dye exists in its lactone leuco
form, while when the solvent melts, the salt dissociates, the pH
inside the microcapsule lowers, the dye becomes protonated, its
lactone ring opens, and its absorption spectrum shifts drastically,
therefore it becomes deeply violet. In this case the apparent
thermochromism is in fact halochromism. [0028] Azobenzene [0029]
The wavelengths at which isomerization occurs depends on the
particular structure of each azo molecule, but they are typically
grouped into three classes: the azobenzene-type molecules, the
aminoazobenzenes, and the pseudo-stilbenes. These azos are yellow,
orange, and red, respectively, owing to the subtle differences in
their electronic absorption spectra. The compounds similar to the
unsubstituted azobenzene exhibit a low-intensity n-p* absorption in
the visible region, and a much higher intensity p-p* absorption in
the ultraviolet. Azos that are ortho- or para-substituted with
electron-donating groups (such as aminos), are classified as
aminoazobenzenes. The pseudo-stilbene class is characterized by
substituting the 4 and 4' positions of the two azo rings with
electron-donating and electron-withdrawing groups (that is, the two
opposite ends of the aromatic system are functionalized). The
addition of this push-pull configuration results in a strongly
asymmetric electron distribution, which modifies a host of optical
properties. In particular, it shifts the absorption spectra of the
trans and the cis isomers, so that they effectively overlap. Thus,
for these compounds a single wavelength of light in the visible
region will induce both the forward and reverse isomerization.
Under illumination, these molecules cycle between the two isomeric
states. [0030] Diazonium [0031] Diazonium salts are light sensitive
and break down under near UV or violet light. This property has led
to their use in document reproduction. In this process, paper or
film is coated with a Diazonium salt. After contact exposure under
light, the residual Diazo is converted to a stable Azo dye with an
aqueous solution of coupler.
[0032] Other typical substances that are photosensitive are
metallic salts, alkali salts and certain halides.
[0033] The list of laser/light reactive materials outlined above is
not intended to be limiting. US 20060241225 describes in further
detail suitable laser activated thermochromic compositions that
could be used to form the dots of this first preferred embodiment.
In US 20060241225A, the thermochromic compositions comprise a
binder polymer, a thermochromic dye and a stabilizer. The
composition is responsive to exposure to a laser beam by undergoing
an irreversible colour change. The laser reactive colour changing
properties of the compounds used in the first preferred embodiment
will consist of a unique compound manufactured from several of the
available materials, including polymers and other materials as
required, to suit the requirement of the substrate used in the
particular embodiment.
[0034] The substrates 2a and 3a, which may be of polycarbonate,
each carry a spiral track that is tracked by the reading and
writing mechanism of the optical drive so as to align the laser
correctly. The spiral track may be embossed on the inner sides of
the substrates 2a, 3a. Conventional optical discs carry such a
track on their data sides. However, the optical disc of this
embodiment differs from conventional optical discs by having a
similar track on the label side 3.
[0035] The substrates 2a, 3a also carry control data in a format
that can be read by an optical disc drive, to convey data about the
optical disc. They may further carry data identifying the
manufacturer of the disc.
[0036] The data side 2 is compliant with an optical disc standard,
and preferably a writable optical disc standard, such as the
minidisk, CD-R, CD-RW, DVD-R, DVD+R, DVD+RW, DVD-RW, DVD-RAM, HD
DVD-R, HD DVD-RAM, BD-R or BD-RE standards.
[0037] The label side 3 may be compliant with an optical disc
standard in so far as is detectable by an optical disc complying
with that standard, during a write operation. Hence, the substrate
3a may comply with that standard. However, the label writing layer
3b need not comply with any optical disc data standard, as it is
not intended that the label is readable by the optical disc drive,
but rather that it is visible to a user. The standard of the label
side 3 need not be the same standard as that of the data side 2,
but preferably both standards are supported by the same optical
drive.
[0038] A method of operation according to an embodiment of the
invention will now be described with reference to FIG. 2. First,
the optical disc 1 is inserted into an optical disc drive with the
label side 3 facing upwards, and data is written to the data side 2
(step S1). Next, the optical disc 1 is removed from the optical
drive and replaced in the optical drive with the label side 3
facing downwards (step S2). The user then outputs one or more data
files to the optical disc drive (step S3). The drive reads the
control information on the label side 3 and thereby identifies the
label side 3 as being writable and conforming to the relevant
standard. The drive then writes the one or more data files to the
label side 3 (step S4), following the track on the substrate
3a.
[0039] The writing operation of the drive on the label side 3
causes the laser of the drive to selectively excite the dots of the
pixels P according to the data content and format of the one or
more data files. Each dot is preferably substantially larger than
the pitch of the spiral track in a radial direction, and is
preferably substantially larger than the writing resolution of the
laser in the circumferential direction. The laser may therefore be
controlled according to the one or more data files to excite a
predetermined proportion of the area of each dot, so as to generate
a desired intensity of each dot. In this way, a colour label may be
created with high colour resolution; in other words, each pixel P
may have any of a wide range of colours and intensities.
[0040] In one preferred embodiment, the label writing layer 3b
includes periodic gaps in the radial direction, containing no
pixels P. In one example, 1 in every 45 tracks in the radial
direction carries no pixels. This feature allows the automatic
error correction of the optical drive to function correctly, even
after the label is written. The gap is preferably sufficiently
intermittent that it does not materially affect the appearance of
the label.
[0041] The step of outputting the one or more data files (step S3)
may include executing a software application to convert a label
design, such as an image file, into the one or more data files
suitable for writing by the optical drive. The software application
may provide a user interface allowing the user to create the label
design. Preferably, the application restricts the design to the
colours, intensities and shape that can be written to the label
writing layer 3b, either during creation of the design or after
completion of the design.
[0042] Once the design is complete, the application then converts
the label design to the one or more data files, according to the
standard to which the label side 3 apparently complies. For
example, the standard may be a writable DVD standard, under which
the relative positions of recorded data on a DVD are predictable
from the content of a data file to be recorded. The one or more
data files preferably comprise a disk image file which represents
both the content and layout of data to be recorded to a disc, such
as an .iso file. The application may determine the relevant
standard by reading the control data from the label side 3.
[0043] The application may output the disk image file for writing
to the optical disc 1. Alternatively, the application may save the
disk image file for subsequent output to the drive by another
application. The disk image file may be distributed, subject to
copyright, and used by others to write the label on other optical
discs in accordance with the embodiment.
[0044] The application may be supplied on a writable disc according
to an embodiment of the invention, preferably a rewritable optical
disc such that the application can be loaded onto a computer and
subsequently rewritten on the disc.
Second Embodiment
[0045] The optical drive of the first embodiment utilises a single
writing laser to write data to a data writing layer of the optical
disk and also to write images to a label writing layer of the
optical disk. As an alternative approach, separate writing devices
could be used to perform the two separate tasks. The writing means
of the first embodiment can still be used to write data to the data
writing layer of the optical disc but a second writing means can be
used to write images to the label writing side of the optical disc.
The second writing means can take the form of a laser writing print
head and such a system will now be discussed below as a second
preferred embodiment of the present invention.
[0046] According to the second preferred embodiment of the present
invention, the laser-reactive printing media 9 is the optical disc
1, and more specifically the label writing layer 3b, and the laser
writing print head is used to write images/patterns on the label
writing layer 3b of the optical disc 1 using a method similar to
that discussed in relation to the second embodiment. In this case
however, the laser writing print head is transported in the radial
direction of the optical disc 1 by the print head transport system
7 whilst the optical disc 1 spins in the circumferential direction
beneath the laser writing print head. In contrast to the optical
drive according to the first embodiment, the laser writing print
head will only write data to the label writing layer 3b of the
optical disc 1 and so a further data writing subsystem is required
to write data to the data writing layer 2b of the optical disc
1.
[0047] FIG. 3 shows a laser writing print head 4, consisting of a
laser array in the form of a print head pattern, according to the
second embodiment of the invention. Laser generating devices 5a,
5b, 5 . . . n are provided in a housing module 6. FIG. 4 shows a
plan view of the arrangement of the laser generating devices 5a,
5b, 5 . . . n showing that they are arranged to form a rectangular
array although the arrangement of the laser generating devices is
not limited in this respect and any other suitable arrangement
could be used.
[0048] The output from each laser generating device 5a, 5b, 5 . . .
n, may be through an aperture in the housing module 6 of any shape
but in a preferred embodiment the apertures is circular. Each laser
generating device 5a, 5b, 5 . . . n is able to direct generated
laser light through its respective aperture so that laser light is
emitted from the housing module 6 and onto suitable laser-reactive
printing media 9 which preferably is the label writing layer 3b of
the optical disc 1 as discussed in relation to the first
embodiment. The label writing layer 3b is positioned a small
distance below the laser writing print head.
[0049] The laser writing print head is mounted on a print head
transport system 7. The laser generating devices 5a, 5b, 5 . . . n
and the print head transport system 7 are electrically connected to
a control module 8. The laser writing print head is transported in
a first direction by the print head transport system 7, whilst the
suitable laser-reactive printing media 9 is transported below the
laser writing print head, in a direction generally orthogonal to
the direction of travel of the laser writing print head. In this
preferred embodiment, the suitable laser-reactive printing media 9
is the label writing layer 3b of the optical disc 1 and the laser
writing print head is transported in the radial direction of the
optical disc 1 by the print head transport system 7 whilst the
optical disc 1 spins in the circumferential direction beneath the
laser writing print head by disc spinning means in the optical
drive.
[0050] The laser generating devices 5a, 5b, 5 . . . n are energised
by the control module 8 such that their laser light falls onto the
label writing layer 3b of the optical disc 1 at the correct
position in the X and Y co-ordinates.
[0051] The laser-reactive material used in the label writing layer
3b of the optical disc 1 may be selected from the same material as
discussed in relation to the first embodiment and has the
significant feature that it will react specifically to the laser
light of the laser generating devices 5a, 5b, 5 . . . n. A single
laser reactive material may be applied uniformly across the label
writing layer 3b of the optical disc 1 if monochrome images are
required. Alternatively, a pattern of dots may be distributed
evenly across label writing layer 3b forming a pattern of dots of
different writing colours: in this case red, green, blue and black,
as discussed in relation to the first embodiment. Each dot
comprises a material that reacts to the laser light of the laser
generating devices 5a, 5b, 5 . . . n by changing from a base colour
(e.g. white or colourless) to the writing colour. Preferably, this
colour change is irreversible or permanent.
[0052] In operation, one or more data files corresponding to images
to be printed on the optical disc are sent via the control module 8
to the print head. The control module 8 converts the data files,
via a similar software application to that discussed in relation to
the first embodiment, into instructions that, when performed by the
laser writing print head, result in a suitable output of the data
file as an image onto the label writing layer 3b of the optical
disc. The control module 8 controls the movement of the laser
writing print head in the radial direction of the optical disc 1
whilst the optical disc is spun in the circumferential direction by
disc spinning means. The control module 8 also controls the output
of laser light from each laser generating device 5a, 5b, 5 . . . n
in the housing module 6, by turning on and off each laser
generating device 5a, 5b, 5 . . . n in a suitable pattern.
[0053] The laser light emitted by the laser generating devices 5a,
5b, 5 . . . n strikes the laser-reactive material of the label
writing layer 3b at a location directly beneath each laser
generating device 5a, 5b, 5 . . . n. If the laser-reactive material
consists of distributed dots of laser reactive materials then the
laser generating devices 5a, 5b, 5 . . . n may therefore be
controlled according to the one or more data files to excite a
predetermined proportion of the area of each dot, so as to generate
a desired intensity of each dot. In this way, a colour label may be
created with high colour resolution; in other words, each dot may
have any of a wide range of colours and intensities. If only a
single laser reactive material has been applied uniformly across
the label writing layer 3b, a monochrome label may be created with
a range of grayscales. In either method a pattern is produced on
the label writing layer 3b beneath the laser writing print head
that corresponds to the laser light output pattern from the laser
generating devices 5a, 5b, 5 . . . n.
Third Embodiment
[0054] The writing operation of the optical drive discussed in
relation to the first embodiment causes the laser of the drive to
selectively excite material reactive to the laser light of the
laser. In the first embodiment, the dots each have different colour
change reactions in response to the laser light e.g. one dot may
turn from white to red whilst another may turn from white to
green.
[0055] In this third embodiment, the label writing layer 3b
comprises a laser reactive material that reacts to laser light by
changing from a base colour (e.g. white or colourless) to a
specific one of a range of writing colours, where the specific
writing colour is dependent on the frequency of the laser light
received. In a preferred embodiment, the material may change to any
one of four colours depending on the frequency of the laser light
received. If the laser reactive material receives a first frequency
of laser light it will change from its base colour to black, if it
receives a second frequency of laser light it will change from its
base colour to magenta, if it receives a third frequency of laser
light it will change from its base colour to yellow, and if it
receives a fourth frequency of laser light it will change from its
base colour to cyan. Preferably, this colour change is irreversible
or permanent.
[0056] The laser reactive material may be formed from one or more
laser-writable inks. The laser reactive material may be one of the
materials discussed in relation to the first embodiment of the
invention, or may be a different laser reactive material. In both
cases, the laser reactive material will react only when excited by
specific designated frequencies.
[0057] The material may be continuous or may comprise discrete
pixels P distributed substantially evenly over the writable surface
of the label writing layer 3b.
[0058] As shown in FIG. 5, rather than having a single laser to
write information to the label layer 3b of the optical disc 1, a
write head is formed by a movable assembly 9 containing two laser
generating devices, 10, 11 and a colour recognising sensor 12. The
movable assembly 9 is able to be moved over the surface of the
label layer 3b in a similar manner to the writing laser of the
first embodiment.
[0059] Each individual laser generating device 10, 11 can be
selectively controlled to output laser light of a single
fundamental frequency. The frequency of the laser light output by
the first laser generating device 10 is different to the frequency
of the laser light output by the second laser generating device 11.
The output laser light from each laser generating device 10, 11, is
passed through respective focussing and collimating lens assemblies
13, 14 arranged so that the laser beams can be collimated and then
focussed on the same point. The collimated laser beams are focused
at the same point on a mirror 15. Heterodyning of the two optical
signals occurs at their point of intersection 16 on mirror 15.
Heterodyning is a well known physical effect and will not be
described in further detail here.
[0060] As a result of the heterodyning of the two optical signals,
each of which has a different frequency, the resultant heterodyned
optical signal reflected from the mirror 15 contains light at four
frequencies that are, respectively:
1. the frequency of the laser light generated by the first laser
generating device 10; 2. the frequency of the laser light generated
by the second laser generating device 11; 3. the sum of the
frequencies of the laser light generated by the first and second
laser generating devices 10, 11; and 4. the difference between the
frequencies of the laser light generated by the first and second
laser generating devices 10, 11.
[0061] The four frequencies of light generated by heterodyning the
outputs of the first and second laser generating devices 10, 11
correspond to the first, second, third, and fourth frequencies of
laser light that cause the material of the optical disc to change
colour from its base colour to either black, magenta, yellow, or
cyan (as discussed above).
[0062] A variable optical filter 17 is provided which receives and
selectively filters the heterodyned optical signal reflected from
the mirror 15. The variable optical filter 17 is adjustable and is
arranged to allow only light having a specific frequency to pass
through at any one time. The optical signal output from the
variable optical filter 17 illuminates a portion of the optical
disc.
[0063] The control module 8 of the optical drive is able to control
the variable optical filter 17 so that only a selected one of the
four frequencies of light contained in the heterodyned optical
signal is allowed to pass through the variable optical filter 17 to
illuminate the portion of the optical disc 1.
[0064] The variable optical filter 17 may comprise an optical
splitter that is able to spatially separate optical signals of
different frequencies, and a selectively controlled shutter array,
aligned with the spatially separated optical signals. As the
heterodyned optical signal passes through the optical splitter, the
four optical signals therein, each having one of the frequencies
discussed above, are diffracted by different amounts dependent on
their frequency. Thus, four individual beams of laser light are
output from the optical splitter, each beam separated from the
others by a fixed distance. The shutters of the shutter array are
aligned with these beams so that one shutter is centered in the
beam path of each spatially separated laser beam. When a shutter is
in an open position, its respective spatially separated laser beam
is allowed to pass unhindered. When a shutter is in a closed
position, its respective spatially separated laser beam is blocked.
The control module 8 can control the individual shutters of the
shutter array to produce any combination of open and closed
individual shutters.
[0065] It can be seen therefore that the specific colour change of
the material beneath the writing head is dependent on which one of
the four frequencies of light contained within the heterodyned
optical signal is allowed to activate the laser reactive
material.
[0066] The colour recognising sensor 12 provided in the write head
is focused on the portion of the optical disc 1 that has the
selectively filtered optical signal applied to it. The colour
recognising sensor 12 is able to detect and measure the colour
change of the material.
[0067] In operation, the write head is moved to the required
position over the label layer 3b of the optical disc 1 in a similar
manner to that described in relation to the first embodiment. Once
the write head is positioned at the required coordinates, the first
and/or the second laser generating device 10, 11 is/are
activated.
[0068] If only the first laser generating device 10 is energised,
the laser beam so produced is collimated and focussed, by
collimating and focussing assembly 14, onto the mirror 15. The
laser beam is reflected from the mirror 15, through the variable
optical filter 17 (which is selectively controlled by control
module 8 to allow light having the frequency of the laser light
generated by the first laser generating device 10 to pass through)
and illuminates a portion of the optical disc 1.
[0069] If only the second laser generating device 11 is energised,
the laser beam so produced is collimated and focussed, by
collimating and focussing assembly 13, onto the mirror 15. The
laser beam is reflected from the mirror 15, through the variable
optical filter 17 (which is selectively controlled by control
module 8 to allow light having the frequency of the laser light
generated by the second laser generating device 11 to pass through)
and illuminates a portion of the optical disc 1.
[0070] If both the first and second laser generating devices 10, 11
are energised, each respective laser beam so produced is collimated
and focussed, by respective collimating and focussing assemblies
13, 14, onto a coincident point on the mirror 15. Heterodyning of
the two optical signals occur at their point of intersection 16 on
the mirror 15 and an optical signal containing the four frequencies
outlined above is reflected from the mirror 15, to the variable
optical filter 17. Control module 8 selectively controls the
variable optical filter 17 to allow light having only one of the
four frequencies to pass through. and illuminate a portion of the
optical disc 1.
[0071] In each case, the material illuminated by the laser light
output from the variable optical filter 17 changes to one of either
black, magenta, yellow, or cyan depending on, which of the four
frequencies of light in the heterodyned optical signal it
receives.
[0072] The colour recognizing sensor 12 monitors the colour change
of the material as a result of the laser illumination and, when the
material has turned to an appropriate colour as recognised by the
colour sensor 12, the colour sensor 12 provides a signal to the
control module 8 which, in turn, de-energises the or both laser
generating devices 10, 11 and instructs a positioning mechanism to
move the write head to the next writing position.
Fourth Embodiment
[0073] The image writing apparatus and method described in relation
to the fourth embodiment is similar to the image writing apparatus,
and the operation thereof, discussed in relation to the first
embodiment.
[0074] As shown in FIG. 6, the data side 2 of the optical disc 1 of
the fourth embodiment is the same as that discussed in relation to
the first embodiment but the arrangement of the label side 3 of the
optical disc 1 is different. The label side is arranged to carry a
visible pattern written thereto by the optical disc drive; it
comprises a substrate 3a and a label writing layer 18 arranged
above the substrate layer 3a. As shown in FIGS. 6 and 7, the label
writing layer 18 comprises four coloured layers 19a, 19b, 19c, 19d,
stacked one on top of the other. The four coloured layers 19a, 19b,
19c, 19d, in this preferred embodiment, are arranged in the
following order as seen from the surface of the optical disc 1: a
white layer 19a, a magenta layer 19b, a yellow layer 19c, and a
cyan layer 19d. Each of these four coloured layers 19a, 19b, 19c,
19d is opaque so that the coloured layer 19a, 19b, 19c, 19d beneath
another coloured layer is not visible. A writing head is provided
comprising a writing laser 20 and a colour recognising sensor 21.
The writing head is movable about the surface of the label side 3
of the optical disc 1, via control module 22 and positioning means
(not shown in FIG. 7). The write position of the laser writing head
is determined by the rotational position of the optical disc 1 and
the radial position of the laser writing head. The drive motors for
the rotational movements of the optical disc 1 and radial movements
of the laser writing head, respectively, may be of the stepper
motor type that will be controlled by software and/or control
module 22 to effect positioning of the laser to the desired writing
point.
[0075] The four coloured layers 19a, 19b, 19c, 19d comprise
material that is thermally reactive to the laser light of the
writing laser 20. When illuminated by the writing laser 20, the
portion of the illuminated coloured layer 19a, 19b, 19c, 19d
beneath and closest to the laser beam absorbs the energy of the
laser beam and vaporises. A colour recognising sensor 21 is
incorporated into the optical drive and it is arranged so that it
is able to detect any colour change seen on the label writing layer
18 of the optical disc 1 at the position illuminated by the laser
beam of the optical drive.
[0076] In operation, the one or more data files corresponding to
images to be printed on the optical disc 1 are sent via the control
module 22 to the writing laser 20. The control module 22 controls
the movement of the laser writing print head in the radial
direction of the optical disc 1 whilst the optical disc is rotated
in the circumferential direction by disc spinning means. The
control module 22 also controls the output of laser light from the
writing laser 20, by turning on and off the writing laser 20 in a
suitable pattern.
[0077] The laser light emitted by the writing laser 20 strikes the
upper-most of the coloured layers (i.e. the coloured layer in
closest proximity to the writing laser--initially this would be the
white layer 19a) of the label writing layer 18 at a location
directly beneath the writing laser 20. The material of the white
layer 19a directly beneath the writing laser 20 absorbs the energy
of the laser beam and, upon absorbing a sufficient amount of
energy, vaporises forming a hole 23 of the same diameter as the
illuminating laser beam. The coloured layer beneath the upper-most
layer (in this case the magenta layer 19b) is then exposed to the
laser beam via the hole 23 in the white layer 19a. Once the area of
the magenta layer 19b illuminated by the laser beam has absorbed
enough energy from the laser beam, it too will be vaporised
exposing the coloured layer beneath (i.e. the yellow layer 19c) and
the process will continue.
[0078] The colour sensor 21 monitors the colour of the area of the
label writing layer 18 directly beneath the writing laser 20. The
colour of this area, as seen by the colour sensor 21 will progress
through the respective colours of the coloured layers 19a, 19b,
19c, 19d (i.e. from white to magenta, from magenta to yellow, then
from yellow to cyan) as each coloured layer is exposed through the
hole 23 vaporised in the coloured layer above. When the colour
sensor 21 detects that the desired colour has been produced, i.e.
that the writing laser 20 has vaporised a hole 23 through
sufficient of the covering coloured layers 19a, 19b, 19c, 19d to
expose the desired coloured layer, it will generate a signal to the
control module 22 which will de-energise the writing laser 20 and
instruct the positioning mechanism to move the write head to the
next writing position.
Alternative Embodiments
[0079] In addition to the variants mentioned above, other variants
are envisaged as falling within the scope of the invention. For
example, the optical disc 1 may be a multi-layer disc, such that
the data writing layer and the label writing layer are on the same
side of the disc and are independently addressable by the optical
drive in the first embodiment, the data writing means and laser
writing print head in the second embodiment, or the laser writing
heads in the third and fourth embodiments, respectively.
[0080] The skilled man will understand that the laser writing print
head of the second embodiment, could be used in other devices
rather than an optical drive. For example, the laser writing print
head could be used in place of a standard print head in a standard
printer. The laser generating devices 5a, 5b, 5 . . . n may be
arranged in the same positions that impact pins would be on the
print head of a standard impact printer, or in the same positions
that the inkjet nozzles would be on the print head of a standard
inkjet printer. In this alternative embodiment, the label writing
layer 3b of the optical disc 1 would be replaced with a
laser-reactive printing media 9. The laser-reactive printing media
might have the dimensions of a standard sheet of paper but need not
be limited in this respect. It will however, incorporate
laser-reactive materials in a similar manner to that as discussed
with reference to the label writing layer in the first and second
embodiments. Images/patterns could be written in a manner similar
to that described in relation to the second embodiment. In this
case however, the laser writing print head is transported in a
first direction by a print head transport system whilst the
laser-reactive printing media would be transported, beneath the
laser writing print head, and in a direction generally orthogonal
to the direction of travel of the print head, by a suitable media
transport mechanism.
[0081] A printer incorporating such a laser writing print head has
several advantages over the prior art systems of laser marking.
Firstly, the laser energy required to mark the laser-reactive
printing media 9 is much less than in other laser marking systems
due to the close proximity between the laser writing print head and
the laser-reactive printing media 9. This also means that lower
energy laser generating devices 5a, 5b, 5 . . . n can be used in
the laser writing print head, providing savings in both energy and
cost efficiencies. Since the layout of the laser generating devices
5a, 5b, 5 . . . n in the laser writing print head conforms to the
placement of the pins in a standard impact printer or the ink
nozzles in a standard inkjet printer, no bespoke software is
required to operate the print head. Software instructions that are
operable to control a standard impact or inkjet printer can be
converted within the control module 8 into instructions that are
suitable for controlling the laser writing print head to produce a
similar output on the laser-reactive printing media 9 as a standard
printer would on normal paper.
[0082] Although the second embodiment and further modifications
discuss a laser writing print head having an array of laser
generating devices 5a, 5b, 5 . . . n, the skilled man will
appreciate that optical fibres could take the place of the
individual laser generating devices 5a, 5b, 5 . . . n so that an
open end of each fibre is arranged into an array. The other end of
each optical fibre could be supplied with laser light from a single
laser, via a suitable optical switching mechanism, so that laser
light is emitted from the open end of the optical fibres onto the
laser-reactive printing media in a suitable pattern.
[0083] The skilled person will also appreciate that the laser
writing print head of the second embodiment (and the alternative
variations of the same discussed above, e.g. a printer
incorporating the laser writing print head) could be arranged to
use the lasers and laser reactive media discussed in relation to
the third and fourth embodiments. For example, the laser writing
print head housing could contain two laser generating devices for
each aperture in the housing. The outputs of each pair of lasers
could be arranged to be heterodyned together and optically filtered
so that only one of the discrete range of laser light frequencies
so produced would leave the aperture in the housing and illuminate
the laser reactive media. The laser reactive media would react to
the specific frequency of light it receives, in positions
corresponding to each aperture of the laser writing print head.
[0084] Alternatively, the laser writing print head of the second
embodiment (and its variations mentioned above) could incorporate
the laser and laser reactive materials of the fourth embodiment.
The laser writing print head housing would contain a single laser
and colour recognising sensor to operate through each laser
aperture in the housing (although a single laser device could
alternatively be used, supplying its laser light to each aperture
via individual optic fibres in a similar manner as discussed
above). The laser reactive media would be vaporised in a pattern
corresponding to the pattern of the laser apertures in the laser
writing print head housing. The colour produced by the vaporisation
of the laser reactive media beneath an aperture would again be
dependent on how far through the coloured layers the hole vaporised
by each laser beam penetrated.
[0085] The first and second embodiments discuss discrete dots of
several laser-reactive materials each turning a specific colour in
response to being illuminated by laser light of one specific
frequency. The skilled man will appreciate that, alternatively, a
single laser-reactive material could be used that changes colour
depending on the frequency or intensity of the laser light with
which it is illuminated. Suitable laser generating devices, capable
of adjusting the intensity of their output beam or the frequency of
the laser light produced, could be used in conjunction with this
material, using a method similar to that disclosed in relation to
either the first or second embodiment. In this case, the
laser-reactive material would be spread evenly over the image
writing layer of an optical disc or printing media and the image
writing means of the first embodiment or the laser writing print
head of the second embodiment could form images on the disc or
media by illuminating the laser-reactive material with different
frequencies, colours, and intensities of laser light. A suitable
software application would convert data files corresponding to the
images to be drawn into suitable instructions to the writing means,
including information concerning frequency and intensity.
[0086] Referring to the variable optical filter 17 of the third
embodiment, the skilled person will understand that a series of
selectively controlled optical filters could be used.
Alternatively, a series of optical filters, each one arranged to
block a specific frequency of laser light could be incorporated in
place of the variable optical filter 17. One or more of the series
of optical filters could be moved into the optical path of the
optical beam reflected from the mirror 15 in order to selectively
filter the reflected beam.
[0087] The skilled person will also understand that the laser
generating devices of the third embodiment need not be selectively
energised. Instead, both of the laser generating devices may simply
always be activated in unison, i.e. so that the variable optical
filter 17 always receives a heterodyned optical signal. The
variable optical filter 17 will filter out the undesired
frequencies in the manner described above.
[0088] The skilled person will understand that any type of variable
optical filter could be used in the third embodiment of the
invention. For example, waveguides could be used to spatially
separate the heterodyned optical signal into individual signals
having discrete frequencies as discussed above. Any apparatus able
to selectively block and unblock the transmission of these
spatially separated optical signals could be used as part of the
variable optical filter 17.
[0089] Although collimating and focussing assemblies have been
described in relation to the third embodiment, the skilled person
will appreciate that, depending on the laser beam dimensions,
focussing may not be necessary and the laser beams can simply be
directed.
[0090] Referring to the colour sensor of the third embodiment,
rather than being used continuously to monitor the colour change of
the laser reactive material, the colour sensor may be used only for
calibration of the system. Calibration might involve calculating a
time needed for a particular frequency of laser light to illuminate
the laser reactive material before the associated colour change
takes place. In this respect, during normal writing operation, the
control module would cause the laser write head to illuminate a
portion of the optical disc for the calculated time, dependent on
the frequency of laser light being used at that specific time and
location, before moving the write head to the next position.
[0091] A colour recognising sensor has been described in relation
to the third and fourth embodiments. The skilled person will
understand, however, that a colour recognising sensor might not be
needed at all if the laser reactive material used in these
embodiments were limited to a known type of material exhibiting a
known reaction (e.g. colour change) in response to the laser
light.
[0092] Referring to the optical disc of the fourth embodiment, the
skilled person will appreciate that the description of the colours
of the coloured layers 19a, 19b, 19c, 19d is merely illustrative
and any arrangement of coloured layers could be used. In addition,
the coloured layers could be any colour, different to those already
mentioned. Rather than having a white coloured layer 19a uppermost
on the surface of the optical disc, the uppermost layer could
instead be black. Also, the laser reactive material of the coloured
layers of the optical disc could incorporate particles that are
adapted to absorb infra-red energy from the laser beam thereby
aiding vaporisation of the laser reactive material. Additionally,
the material of the coloured layers of the fourth embodiment may
need to absorb different quantities of energy from the laser beam
before they vaporise. In such a case, the laser writing head may be
adapted to increase or decrease the power of the laser beam
depending on the colour of the laser reactive material to be
vaporised (as detected by the colour sensor).
[0093] The above embodiments illustrate, but do not limit, the
present invention. Alternative embodiments which may occur to the
skilled reader on reading the above description may also fall
within the scope of the invention.
* * * * *