Optical print head using a glass arm waveguide

This invention relates to an optical mechanism comprising: an optical beam generating mechanism to generate an optical beam; and a unitary, transparent waveguide for guiding the optical beam to an optically writable surface wherein optical elements for guiding the optical beam are coated onto the waveguide to create a relatively compact optical system, a relatively low exit numerical aperture for the exit pupil, and for bending and re-directing the optical beam.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an optical mechanism comprising: an optical beam generating mechanism to generate an optical beam; and a unitary, transparent waveguide for guiding the optical beam to an optically writable surface wherein optical elements for guiding the optical beam are coated onto the waveguide to create a relatively compact optical system, a relatively low exit numerical aperture for the exit pupil, and for bending and re-directing the optical beam.

2. Description of the Related Art

Prior to the present invention, as set forth in general terms above and more specifically below, it is known that optical disc drives have historically been used to optically read data from and optically write data to data regions of optical discs. More recently, optical disc drives have been used to optically write images to label regions of optical discs. For example, a type of optical disc is known in which a laser or other optical beam can be used to write to the label side of an optical disc.

A costly component of an optical disc drive is the optical pickup unit (OPU). The OPU is the optical mechanism by which an optical beam is generated, and then guided to the surface of an optical disc using a number of precisely arranged lenses and other components, including an objective lens, which have to be manufactured to high tolerances, and thus at high cost. Therefore, optical disc drives typically only have one OPU for cost and complexity reasons. An optical drive having just a single such optical mechanism for accessing both the label and the data sides of an optical disc, however, forces a user to remove the disc from the drive, flip it over, and reinsert the disc back into the drive when the optical drive needs to access the data side after having accessed the label side, and vice-versa. Consequently, a more advantageous optical disc drive, then, would be provided if only one OPU could be utilized.

It is also known, that conventional optical print heads (OPHs) use a non-waveguide optical path in the optical disk drive. The non-waveguide optical path can be constructed of plastic or metallic materials. The discrete optical components (objective lens, collimator, prism, and quarter wave element) are then cemented to the non-waveguide arm or optical pick-up unit (OPU)-sled assembly. The alignments of these optical components are very critical to the quality of the OPH. Also, the alignments can be costly as well as time consuming. Therefore, a further advantageous OPH, then, would be provided if a glass/quartz (or any high transmit and low birefringence material for labeling wavelength) are could be used in the OPH for disk labeling.

It is further known to use a unitary wave guide arm wherein optical elements are secured to the wave guide to provide the necessary reflection/refraction surfaces. As discussed above, the optical elements alignments and optical beam generating mechanism alignments are very critical to the quality of the OPH. Also, the alignments can be costly as well as time consuming. Finally, these type of wave guides utilize an extremely long path length.

It is apparent from the above that there exists a need in the art for a unitary, transparent glass/quartz (or any high transmit material for labeling wavelength) waveguide that utilizes optical elements that are placed onto the waveguide such that the waveguide creates a more compact assembly, employs a relatively low numerical aperture for the exit pupil that can be used in the OPH for disk labeling, and reduces the number of alignments. It is a purpose of this invention to fulfill this and other needs in the art in a manner more apparent to the skilled artisan once given the following disclosure.

SUMMARY OF THE INVENTION

Generally speaking, an embodiment of this invention fulfills these needs by providing an optical mechanism comprising: an optical beam generating mechanism to generate an optical beam; and a unitary, transparent waveguide for guiding the optical beam to an optically writable surface wherein optical elements for guiding the optical beam are coated onto the waveguide to create a relatively short optical beam path length, a relatively low numerical aperture for the exit pupil, and for bending and re-directing the optical beam.

In certain preferred embodiments, the optical beam generating mechanism is capable of generating an optical beam through the use of a laser diode. Also, the waveguide is constructed of any suitable moldable material upon which the optical elements such as multilayer anti-reflective, polarization separation coatings and reflective coatings can be placed such that the coatings have a high enough transmission and low enough birefringence. Finally, the optical mechanism measures characteristics of that beam as it is reflected back from the optically writable surface.

In another further preferred embodiment, a unitary, transparent glass/quartz (or any high transmit material and low birefringence for labeling wavelength) waveguide that utilizes optical elements that are placed onto the waveguide such that the waveguide creates a more compact assembly, employs a relatively low numerical aperture that can be used in the OPH for disk labeling, reduces the number of disparate optical elements, and reduces the number of alignments is disclosed.

The preferred optical mechanism, according to various embodiments of the present invention, offers the following advantages: lightness in weight; a more compact assembly; a relatively low numerical aperture; and decreased optical element/optical beam generating mechanism alignment complexity. In fact, in many of the preferred embodiments, these factors of shorter optical beam path length, lower numerical aperture, and decreased optical element/optical beam generating mechanism alignment complexity are optimized to an extent that is considerably higher than heretofore achieved in prior, known optical mechanisms.

The above and other features of the present invention, which will become more apparent as the description proceeds, are best understood by considering the following detailed description in conjunction with the accompanying drawings, wherein like characters represent like parts throughout the several views and in which:

DETAILED DESCRIPTION OF THE INVENTION

With reference first toFIG. 1, there is illustrated one preferred embodiment for use of the concepts of this invention.FIG. 1shows an optical disc drive100, according to an embodiment of the invention. The optical drive100is for reading from and/or writing to an optical disc102which has a label side104A opposite a data side104B. More specifically, the optical drive100is for reading from and/or writing to an optically writable label side104A of the optical disc102, and/or an optically writable label side104B of the optical disc102, which are collectively referred to as the sides104of the optical disc102.

The optically writable data side104B of the optical disc102includes a data region on which data may be optically written to and/or optically read by the optical drive100. The data side104B is thus the side of the optical disc102to which binary data readable by the optical drive100and understandable by a computing device is written, and can be written by the optical drive100itself. For instance, the data side104B may be the data side of a compact disc (CD), a CD-readable (CD-R), which can be optically written to once, a CD-readable/writable (CD-RW), which can be optically written to multiple times, and so on. The data side104B may further be the data side of a digital versatile disc (DVD), a DVD-readable (DVD-R), or a DVD that is readable and writable, such as a DVD-RW, a DVD-RAM, or a DVD+RW. The data side104B may further be the data side of a high-capacity optical disc, such as a Blu-ray optical disc, and so on. Furthermore, there may be a data region on each side of the optical disc102, such that the optical disc is double sided, and such that there is a label region on at least one of the sides of the disc.

The optically writable label side104A of the optical disc102includes a label region on which an image may be optically written thereto, to effectively label the optical disc102. The label side104A is thus the side of the optical disc102to which visible markings can be optically written to realize a desired label image. It is noted in one embodiment that both the sides104A and104B of the optical disc102may have both label regions and data regions.

The optical drive100is depicted inFIG. 1as including an optical mechanism106. Different and specific embodiments of the optical mechanism106are described in detail later in the detailed description. In general, however, the optical mechanism106does not employ an objective lens, and further employs a unitary, transparent waveguide to direct a generated optical beam to the surface of the optical disc102. As such, the optical mechanism106is advantageous because it may not need costly, complex, and precisely arranged lenses and other components.

In particular, the optical mechanism106employing a unitary, transparent waveguide, and not employing an objective lens, is applicable to using the optical mechanism106to optically write to the label side104A of the optical disc102, because less precision is needed to optically write to and/or read from the label side104A, as opposed to optically writing to and/or reading from the data side104B. In such an embodiment of the invention, the optical mechanism106may be referred to as an optical print head, because it is used to optically write marks to the label side104A, to achieve a desired image on the label side104A of the optical disc102. However, in other embodiments, the optical mechanism106may also be able to be used to optically write to and/or read from the data side104B, too.

The optical drive100is also depicted inFIG. 1as including a spindle110A and a spindle motor110B, which are collectively referred to as the first motor mechanism110. The spindle motor110B rotates the spindle110A, such that the optical disc102correspondingly rotates. The first motor mechanism110may include other components besides those depicted inFIG. 1. For instance, the first motor mechanism110may include a rotary encoder or another type of encoder to provide for control of the spindle motor110B and the spindle110A.

The optical drive100is further depicted inFIG. 1as including a sled114A, a coarse actuator114B, a fine actuator114C, and a rail114D, which are collectively referred to as the second motor mechanism114. The second motor mechanism114moves the optical mechanism106to radial locations relative to a surface of the optical disc102. The coarse actuator114B is or includes a motor that causes the sled114A, and hence the fine actuator114C and the optical mechanism106situated on the sled114A, to move radially relative to the optical disc102on the rail114D. The coarse actuator114B thus provides for coarse or large radial movements of the fine actuator114C and the optical mechanism106.

By comparison, the fine actuator114C also is or includes a motor, and causes the optical mechanism106to move radially relative to the optical disc102on the sled114A. The fine actuator114C thus provides for fine or small movements of the optical mechanism106. The second motor mechanism114may include other components besides those depicted inFIG. 1. For instance, the second motor mechanism114may include a linear encoder or another type of encoder to provide for control of the coarse actuator114B and the sled114A. Note that it is possible to use a single motor for both actuations, under the condition that it has enough accuracy to provide acceptable print quality to the human eye. This single motor may or may not use an encoder strip to provide feedback to enhance accuracy of positioning and hence print quality. Furthermore, either or both of the motor mechanisms110and114may be considered as the movement mechanism of the optical drive100.

It is noted that the utilization of a fine actuator114C and a coarse actuator114B, as part of the second motor mechanism114, is representative of one, but not all, embodiments of the invention. That is, to radially move the optical mechanism106in relation to the optical disc102, the embodiment ofFIG. 1uses both a fine actuator114C and a coarse actuator114B. However, in other embodiments, other types of a second motor mechanism114C can be used to radially move the optical mechanism106in relation to the optical disc102, which do not require both a fine actuator114C and a coarse actuator114B. For instance, a single actuator or other type of motor may alternatively be used to radially move and position the optical mechanism106in relation to the optical disc102. One such alternative embodiment is described later, at the end of the detailed description.

The optical drive100is additionally depicted inFIG. 1as including a controller116. The controller116can in one embodiment include at least a rotation controller116A, a coarse controller116B, and a fine controller116C. The mechanisms116may each be implemented in software, hardware, or a combination of software and hardware. The rotation controller116A controls movement of the spindle motor110B, and thus controls rotation of the optical disc102on the spindle110A, such as the angular velocity of the rotation of the optical disc102. The coarse controller116B controls the coarse actuator114B, and thus movement of the sled114A on the rail114D. The fine controller116C controls the fine actuator114C, and thus movement of the beam source106A on the sled114A.

The controller116may further include other components besides those depicted inFIG. 1. For instance, the controller116can be responsible for turning on and off, and focusing, the optical beam316(FIG. 3). In addition, as can be appreciated by those of ordinary skill within the art, the components depicted in the optical drive100are representative of one embodiment of the invention, and do not limit all embodiments of the invention.

FIG. 2shows the optical mechanism106of the optical disc drive100in detail, according to an embodiment of the invention. The optical mechanism106includes carriage rails202, an optical beam generating mechanism204, a carriage206, and unitary, transparent waveguide208. The carriage rails202are rigidly connected to fine actuator114C (FIG. 1). Carriage rails202, preferably, are constructed of any suitable, durable material. Carriage206is rigidly connected to carriage rails202. Carriage206, preferably, is constructed of any suitable, durable material. Optical beam generating mechanism204is rigidly connected to carriage206. Optical beam generating mechanism204, preferably, includes a conventional laser diode that is capable of emitting a laser beam304(FIG. 3). One example of this diode is Sharp Corporation Japan's GH07P28 series of laser diodes. Unitary, transparent waveguide208is rigidly connected to carriage206such that an optical beam304originating from optical beam generating mechanism204can be traversed through waveguide208such that it interacts with the label side104A of the optical disc102to produce marking. Waveguide208, preferably, is constructed of any suitable, durable, transparent material that is capable of being molded. In particular, waveguide208is a single block of glass or polymeric material which provides all of the focusing optics and folding mirrors built in a single molded step. The multilayer coatings are placed on the waveguide after the molding process is complete. The multilayer coatings can be placed between two molding processes. Multilayer coatings provide mirror areas for the reflective optics and mirrors and areas of high transmission for light entering from the optical beam generating mechanism204and exiting onto label side104A. The multilayer coatings can also create a beam splitter, a polarized beam splitter, an anti-reflective layer and other such reflective optics. Preferably, the total thickness required for optical mechanism106is 6.45 millimeters with a conventional 5.6 millimeter diameter optical beam generating mechanism204. It is to be understood that other packages are available that can reduce this distance even further. It is to be further understood that since all the optics are formed in one molded step, the cost is very low and optical element alignment errors are reduced. Finally, the waveguide208creates a relatively compact optical system that exhibits low birefringence, a relatively low exit numerical aperture for the exit pupil, and for bending and re-directing the optical beam.

FIG. 3shows the optical mechanism106in detail, according to another embodiment of the invention. Like-numbered components betweenFIG. 3andFIG. 2operate at least substantially the same between the optical mechanisms106ofFIGS. 2 and 3, and the description of such components is not repeated in relation toFIG. 3unless the manner by which they operate is different in relation toFIG. 3.

With respect toFIG. 3, waveguide208is illustrated. Waveguide208includes, in part, multi-layer, anti-reflective coating or lens306, multi-layer reflective coating310, multi-layer, anti-reflective coating or lens314, and conventional laser beam sensor318. During the construction of waveguide208, waveguide208is molded. Portions of waveguide208are conventionally covered so that only the areas where anti-reflective coatings or lenses are to be placed are left uncovered. The anti-reflective coatings or lenses are then conventionally applied. It is to be understood that the anti-reflective coating or lens should be designed to work with the wavelength of interest. Also, the anti-reflective areas are conventionally covered and a reflective coating is conventionally placed on the remainder of waveguide208. It is to be further understood that the reflective coating should be designed to work with the wavelength of interest. Finally, it is to be understood that an anti-reflective coating or lens is equal to a high transmission coating or lens. This means that a light beam will transmit through. On the other hand, a reflective coating highly reflects the light beam in an opposite direction such that no light beam is transmitted through.

During the operation of optical mechanism106, a laser beam304is emitted from laser diode204. Laser beam304enters into waveguide208and interacts with anti-reflective coating306. Anti-reflective coating306causes the laser beam to transmit through/focus and form laser beam308. Laser beam308interacts with reflective coating310to create laser beam312. Laser beam312interacts with anti-reflective coating314. After laser beam312interacts with anti-reflective coating314, laser beam312is further transmitted through/focused such that laser beam316exits waveguide208and optically writes marks to the label side to achieve a desired image on the label side of the optical disc.

The reflected optical beam320is similarly routed back through waveguide208at curved section322. Curved section322is also coated with the same multi-layer, anti-reflective coating, as discussed above. The reflected optical beam320is transmitted through/focused by curved section322such that it impinges upon conventional laser beam detector/sensor318. The location of laser beam316is then conventionally monitored/adjusted, according to conventional techniques.

FIG. 4shows a side view of carriage rails202, laser diode204, and carriage206. As shown inFIG. 4, laser beam316exits waveguide208and optically writes marks to the label side104A to achieve a desired image on the label side104A of the optical disc102. Preferably, laser beam316should have a width of between 32 μm and 18 μm full width half maximum (FWHM) for proper labeling applications.

FIG. 5shows the intensity profile of the focused beam316(FIG. 3) at the label side104A (FIG. 1). This intensity profile demonstrates that the optical mechanism106can create a suitable intensity of the focused beam316(FIG. 3) at the label side104A (FIG. 1).

FIG. 6shows the irradiance pattern of the focused beam316(FIG. 3) at the label side104A (FIG. 1). This irradiance pattern demonstrates that the optical mechanism106can create a suitable irradiance of the focused beam316(FIG. 3) at the label side104A (FIG. 1).

FIG. 7shows the intensity of the x-intensity profile of the focused beam316(FIG. 3) at the label side104A (FIG. 1).FIG. 8shows the intensity of the y-intensity profile of the focused beam316(FIG. 3) at the label side104A (FIG. 1). Both profiles showed good axisymmetric Gaussian profile shapes.

The optical beam316is output onto the surface of the optical disc102, such as the label side104A, at a spot that may have a circular or an oval shape. In some situations, it may be desired to reduce the size, or the surface area, of this spot, for better precision and to achieve higher pixel density on the surface of the optical disc102. Reducing the size of the spot at which the optical beam212is output from the waveguide208may be modified by changing the waveguide208.

The optical mechanism106has been described as having an optical beam-generating mechanism204that is specifically, or that specifically includes, an optical beam diode, such as a laser diode, which emits an optical beam304that can be a laser beam, for instance. In other embodiments, the optical-beam generating mechanism204may be or include components other than an optical beam diode like a laser diode.

The optical mechanism106of various embodiments of the invention that have been described is at least for optically writing to the label side104A of the optical disc102. In one embodiment, the optical mechanism106may be able to be also employed to optically write to and/or optically read from the data side104B of the optical disc102. In such an embodiment, the optical disc102would have to be removed from the optical disc drive100, flipped or turned over, and reinserted into the optical disc drive100for the optical mechanism106to access the label side104A after the data side104B of the optical disc102has been accessed, and vice-versa. This can be inconvenient for the user, however. In such situations, and in the embodiment where the optical mechanism106cannot be employed to optically write to and/or optically read from the data side104B of the optical disc102, the optical disc drive100may be modified to include two optical mechanisms, including the optical mechanism106.

FIG. 9shows the optical disc drive100, according to such an embodiment of the invention. In particular, the optical disc drive100includes the optical mechanism106that has been described, as well as another optical mechanism902situated or disposed opposite to the optical mechanism106. The other components of the optical disc drive100that are depicted inFIG. 1, such as various motor mechanisms and controllers, are not shown inFIG. 9for illustrative convenience. Furthermore, the optical disc drive100ofFIG. 9may have additional components besides those depicted inFIG. 9, such as one or more motor mechanisms for the optical mechanism902. The optical mechanism106is incident to the label side104A of the optical disc102that has been inserted into the optical disc drive100, whereas the optical mechanism902is incident to the data side104B of the optical disc102that has been inserted into the optical disc drive100.

As a result, access to both the label side104A and the data side104B of the optical disc102can be achieved by the optical disc drive100, without having to have the user remove the disc102from the drive100, flip it over, and reinsert the disc102into the drive100for the drive100to access the label side104A after having accessed the data side104B, and vice-versa. The optical mechanism106can be in accordance with the embodiments of the invention that have been described, such that it does not employ an objective lens. By comparison, the optical mechanism902in one embodiment can be a conventional optical pickup unit (OPU), and thus employ an objective lens as well as other costly and complex components. In another embodiment, however, the optical mechanism902may be another instance of the optical mechanism106that has been described.

FIG. 10shows a method1000for optically writing an image to the optically writable label side104A of the optical disc102with the optical drive100having the optical mechanism106with the waveguide208that has been described, according to an embodiment of the invention. The method1000may thus be performed by the components of the optical drive100that have been described. At least some components of the method1000may be implemented as computer program parts of a computer program stored on a computer-readable medium. The medium may be a magnetic storage medium, such as a hard disk drive, an optical storage medium, a magnetic optical storage medium such as an optical disc, and/or a semiconductor storage medium, such as a memory, among other types of computer-readable media.

The optical disc102is initially rotated within the optical drive100(step1002). The optical mechanism106is radially moved relative to the optical disc102to cause the optical mechanism106to be incident to a given radial location of a label region of the optical disc102(step1004). For instance, where the optical mechanism106includes the carriage206, the carriage206, that has been described, can be rotated. The label region of the optical disc102can, in one embodiment, be the label side104A of the optical disc102. The optical beam316is then selectively generated by the optical mechanism106(step1006).

The optical beam316is routed to the radial location of the label region of the optical disc102to which the optical mechanism106is incident using the waveguide208, as has been described (step1008). Routing of the optical beam316that is selectively generated and routed to the radial location of the label region of the optical disc102, as the optical disc102is being rotated, therefore enables the optical beam316to optically write to this radial location a portion of an image to be optically written to the label region (step1010). Steps1004,1006,1008, and1010of the method1000are repeated for new radial locations of the label region of the optical disc102, until the desired image has been completely written to the label region of the optical disc102.

It is to be understood that the flowchart of theFIG. 10shows the architecture, functionality, and operation of one implementation of the present invention. If embodied in software, each block may represent a module, segment, or portion of code that comprises one or more executable instructions to implement the specified logical function(s). If embodied in hardware, each block may represent a circuit or a number of interconnected circuits to implement the specified logical function(s).

Also, the present invention can be embodied in any computer-readable medium for use by or in connection with an instruction-execution system, apparatus or device such as a computer/processor based system, processor-containing system or other system that can fetch the instructions from the instruction-execution system, apparatus or device, and execute the instructions contained therein. In the context of this disclosure, a “computer-readable medium” can be any means that can store, communicate, propagate or transport a program for use by or in connection with the instruction-execution system, apparatus or device. The computer-readable medium can comprise any one of many physical media such as, for example, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor media. More specific examples of a suitable computer-readable medium would include, but are not limited to, a portable magnetic computer diskette such as floppy diskettes or hard drives, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory, or a portable compact disc. It is to be understood that the computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a single manner, if necessary, and then stored in a computer memory.

Those skilled in the art will understand that various embodiment of the present invention can be implemented in hardware, software, firmware or combinations thereof. Separate embodiments of the present invention can be implemented using a combination of hardware and software or firmware that is stored in memory and executed by a suitable instruction-execution system. If implemented solely in hardware, as in an alternative embodiment, the present invention can be separately implemented with any or a combination of technologies which are well known in the art (for example, discrete-logic circuits, application-specific integrated circuits (ASICs), programmable-gate arrays (PGAs), field-programmable gate arrays (FPGAs), and/or other later developed technologies. In preferred embodiments, the present invention can be implemented in a combination of software and data executed and stored under the control of a computing device.

It will be well understood by one having ordinary skill in the art, after having become familiar with the teachings of the present invention, that software applications may be written in a number of programming languages now known or later developed.

Although the flowchart of theFIG. 10shows a specific order of execution, the order of execution may differ from that which is depicted. For example, the order of execution of two or more blocks may be scrambled relative to the order shown. Also, two or more blocks shown in succession inFIG. 10may be executed concurrently or with partial concurrence. All such variations are within the scope of the present invention.

Once given the above disclosure, many other features, modifications or improvements will become apparent to the skilled artisan. Such features, modifications or improvements are, therefore, considered to be a part of this invention, the scope of which is to be determined by the following claims.