Labeling optical storage discs, such as (compact discs) CDs, (digital versatile discs) DVDs, and the like, may be accomplished in various ways. One method involves exposing a coating on a disc to light, such as laser light. Exposing the coating to light produces a chemical change in the coating that shows up as visible marks that form a portion of a label. However, this method can take a relatively long time to produce a label.
In the following detailed description of the present embodiments, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments that may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice disclosed subject matter, and it is to be understood that other embodiments may be utilized and that process, electrical or mechanical changes may be made without departing from the scope of the claimed subject matter. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the claimed subject matter is defined only by the appended claims and equivalents thereof.
For one embodiment, a sled 122 carries thermal print head 120. In some embodiments, a drive mechanism 124 moves sled 120 radially on a rail 126. For one embodiment, drive mechanism 124 may include a coarse-adjust motor, such as a stepper motor, that provides a coarse adjustment of the sled 122 and a fine-adjust motor, such as a voice coil motor, that provides a fine adjustment the of sled 122. For another embodiment, a spindle 130 passes through a hole 132, passing through a center of optical disc 110. A spindle motor 134 rotates spindle 130 and thus optical disc 110. For another embodiment, a rotary encoder 136 is connected to spindle motor 134. For some embodiments, spindle motor 134, spindle 130, and rotary encoder 136 constitute a rotational drive mechanism for rotating optical disc 110.
For one embodiment, thermal print head 120 provides thermal energy that heats coating 114 past a critical temperature, thereby producing a chemical change that shows up as an optically visible mark on label side 112 that forms a portion of a label. That is, heating portions (or pixels) of the coating past the critical temperature causes these pixels to turn substantially a single shade of darkness. For another embodiment, various shades of gray may be obtained by using half-toning. For another embodiment, half-toning may include interspersing dark pixels, i.e., pixels exposed to heating, among light pixels, i.e., pixels not exposed to heating, where the percentage of dark to light pixels determines the darkness perceived by a viewer. For some embodiments, thermal print head 120 is kept in direct contact with coating 114, as shown in
For some embodiments, an electromagnetic radiation source 140, such as an ultra-violet light source, e.g., a laser, LED, ultraviolet lamp, or the like, may be used to treat the optically visible marks formed on label side 112. This may be done to increase the life of the marks when using coatings having lower critical temperatures at which the marks form. Note, for example, that without the use of source 140 the life of the marks may be compromised for coatings having lower critical temperatures when the disc is stored in higher temperature environments, such as in automobiles during the summer. For some embodiments, electromagnetic radiation source 140 may expose an entire label at once or may expose the label marks on a track-by-track basis, e.g., by moving electromagnetic radiation source 140 radially using a sled/rail system similar to that for moving thermal print head 120.
A controller 150 controls thermal print head 120, spindle motor 134, encoder 136, drive mechanism 124, and electromagnetic radiation source 140. For another embodiment, controller 150 is coupled to a host 160, such as a main controller of a disc-media marking device, a computer that includes optical disc drive system 100, or the like.
For one embodiment, controller 150 includes a processor 152 for processing computer/processor-readable instructions. These computer-readable instructions are stored on a computer-usable media 154 and may be in the form of software, firmware, or hardware. As a whole, these computer-readable instructions are often termed a device driver. In a hardware solution, the instructions are hard coded as part of a processor, e.g., an application-specific integrated circuit (ASIC) chip. In a software or firmware solution, the instructions are stored for retrieval by the processor 152. Some additional examples of computer-usable media include static or dynamic random access memory (SRAM or DRAM), read-only memory (ROM), electrically-erasable programmable ROM (EEPROM or flash memory), magnetic media and optical media, whether permanent or removable.
For one embodiment, heating elements 210 or heating elements 310 may each comprise two heating elements, a primary heating element and a redundant heating element that would replace the corresponding primary heating element if that primary heating element becomes defective. For one embodiment, the elements in substantially the same location such that the difference in position will not be perceived by a user examining a marked disc. Alternatively the writing time advanced or delayed so as to use the rotation to compensate for the difference in position. For one embodiment, the resistance of the primary heating elements is monitored. For another embodiment, if the monitored resistance of a primary heating element exceeds a predetermined resistance indicative of an open or otherwise defective primary heating element, the corresponding redundant heating element would be activated, and the activation of that redundant heating element would be synchronized accordingly. In other embodiments, instead of using redundant heating elements upon detecting a defective heating element, one of the remaining heating elements may be activated and positioned, using thermal print head 120, to replace the defective heating element in addition to performing its originally intended functions.
For some embodiments, the heating elements may be coated, e.g., using TEFLON or the like, so as not to damage, e.g., mar or scratch, disc 110. For other embodiments, thermal print head 120 may be fabricated from or coated with a material, such as TEFLON, that will not damage disc 110.
For one embodiment, thermal print head 120 is sized to produce a suitable printing resolution, e.g., about 600 dots per inch that corresponds to a pixel size of about 40 microns in diameter. An exemplary size of thermal print head 120 for producing pixels of about 40 microns in diameter would include heating elements on the order of 25 percent smaller in diameter than a target pixel size, e.g., to provide a margin for spreading of the pixel as heat spreads during the marking process.
For some embodiments, the heating elements or thermal print head have a relatively high thermal diffusivity so that a temperature of a heater element or the print head can be heated to a predetermined temperature sufficient to heat the coating above the critical temperature for producing a mark or cooled to a predetermined temperature below the temperature sufficient to heat the coating above the critical temperature for producing a mark within a fraction of a time it takes to form a mark. For another embodiment, the heating elements or thermal print head may be preheated to a temperature that is just below a predetermined temperature sufficient to heat the coating above the critical temperature for producing a mark. For another embodiment, the predetermined temperature may be determined through computer and/or experimental simulations for various operating conditions, e.g., operating temperatures of disc 110, etc.
For some embodiments, thermal print head 120 is adapted so that when thermal print head is in contact with disc 110 the same contact pressure is applied to each of the heating elements, e.g., heating elements 210 or 310. For one embodiment, spring loading of each of the heating elements in the print head 120 accomplishes this.
In some embodiments, the marks may be fully formed in a single pass or revolution of disc 110. Note that a certain amount of heat energy is required at a desired mark location (or pixel) to raise the temperature at this location past the critical temperature to form a mark. Note further that amount of heat energy delivered to a location depends at least in part on the heat output of the heater elements and the time the heater elements are adjacent the desired mark location, which depends on the rotation speed. Therefore, for other embodiments, the same locations on label side 112 of disc 110 are cumulatively heated on each of several revolutions of disc 110 by energizing the heater elements for each revolution of the disc. The cumulative heat imparted to each location produces a mark at that location when the amount of cumulative heat energy transferred to the location is sufficient to bring the temperature past the critical temperature. This process enables higher rotational speeds of disc 110 for a fixed heat output of the heating elements. Note that as the rotational speed increases, the amount of time each location is adjacent a heating element decreases, thus reducing the amount of thermal energy that is transferred to that location for a fixed heat output of the heating element.
When using thermal print head to produce marks at several radial locations on label side 112 of disc 110, such as the entire labelable portion, substantially simultaneously, the tangential velocity is different at each radial location. That is, the tangential velocity increases with the radius. Therefore, for some embodiments, the power applied to the heating elements is increased as the radial location corresponding to the heating elements increases and thus the rate of thermal energy transferred to the different radial locations increases with the radius so that the amount of thermal energy transferred to the different radial locations is substantially the same. Otherwise, if the same power were applied to each heating element, more thermal energy would be transferred to the locations at the lower radii than the higher radii because of the longer times at the lower radii because of the lower tangential velocities. This could result in darker marks at the lower radii.
For one embodiment, synchronizing the energization of the heating elements to the rotation of the disc may be accomplished by generating a write clock, e.g., using a phase locked loop. For example, one clock edge of the write clock, e.g., positive clock edge, may be used to activate a heating element when that heating element is adjacent a pixel to be written, and another clock edge, e.g., a negative, or another positive, clock edge to deactivate the heating element after writing the pixel. Alternatively, an open loop method may be employed. One example of an open-loop method involves accurately controlling the rotational speed of the disc and then triggering the energization of the heating elements based upon a timing signal associated with the disc rotation. For one embodiment, triggering may be accomplished by sensing timing marks (or spokes), such as spoke 410, located within a control feature region 420 on (or visible from) label side 112 of disc 110, as shown in
For some embodiments, encoder 136 (
For one embodiment, sensors 450 and 460 produce an analog output.
Note that the center-to-center spacing of ¼ of the pitch P between sensors 450 and 460 enables a portion of a linear portion of the output of one of the sensors to correspond to a non-linear portion of the other sensor. For example, a portion B of a linear portion of the output of sensor 450 of
Signal 480 is constructed as follows for one embodiment: The absolute value (or magnitude) of the slope is obtained for each linear portion between a maxima and minima of the outputs of sensors 450 and 460, e.g., of the slopes of linear portions A, B, C, D, etc. of
The above procedure is repeated to produce portion X3 of signal 480 between common points F, F′ and G, G′, portion x4 between common points G, G′ and H, H′ of
To control the rotational speed of disc 110, the actual angular distance moved by disc 110 during a predetermined time period, initiated at zero degrees, for example, is determined as described above from the accumulated output of sensors 450 and 460. Dividing the actual distance by the time period gives the actual rotational speed that is compared to, e.g., subtracted from, the desired rotational speed. The rotational speed will be adjusted based on the difference between the desired and actual rotational speeds. The process may be repeated until the difference is at a predetermined value, e.g., substantially zero.
For one embodiment, thermal print head 120 may be moved out of contact with label side 112 of disc 110, as shown in
Although specific embodiments have been illustrated and described herein it is manifestly intended that the scope of the claimed subject matter be limited only by the following claims and equivalents thereof.