Patent Grant
7497534
The present invention relates to printing systems and methods for printing with the same. More particularly, the present invention relates to printing systems with ink jet cartridges that are configured to radially print directly on to the top surface of a circular media that is inserted into a CD drive mechanism, while the CD drive mechanism rotates the media in relation to a printing assembly.
In the art of dispensing fluidic ink objects as it applies to radial printing, there is a need to place ink objects accurately and precisely onto the spinning circular media to effectively use the mechanisms of radial printing. In a radial printing application, ink is placed onto a circular media as it is rotating. To properly place the ink, the mechanisms governing the print process must have as one of its inputs information relating to the instantaneous position of the disk with respect to the print engine emitting the ink. That information over a period of time translates to instantaneous angular position and velocity, which affects other aspects of radial printing such as pen firing frequency. Thus, in any radial printing system, a mechanism must be employed to provide the electronics governing the printing process with the information regarding the instantaneous position of the rotating media or disk.
Accordingly, there is a need for mechanisms for providing an instantaneous angular position of a rotating media for use in printing onto such rotating media.
The present invention relates to information circular recording media, such as an optical disc like CD recordable media (CD-R). For the scope of the present invention, the terms “CD” and “media” are intended to mean all varieties of optical recording devices that record media and their respective media discs, such as CD-R, CD-RW, DVD-R, DVD+R, DVD-RAM, DVD-RW, DVD+RW and the like. More particularly, this invention uses a variety of methods to determine the instantaneous angular position of a spinning and typically circular recordable CD-R media to enable radial printing. This includes: using prerecorded timing information from the native wobble signal in pre-grooved CD-R recordable disc media over the entire prerecorded disc area; using the timing-code information in the data track of an already recorded CD-R disc; using signals from the rotating spindle motor, such as the motor poles and associated Hall Effect sensors; using an encoding pattern from a code wheel on the shaft of the rotating spindle motor; or using an entirely independent encoding pattern pre-placed during manufacturing directly on the inner hub or outer circumference edge of the CD-R media coupled with an external encoder sensor. These signals are uniquely combined with a radial printing system to form a synchronized system for printing a label on the top surface of the recordable disc media while the disc is spinning, independent of recording, during recording or during playback.
The CD Standard Specifications Orange Book specifies in detail how CD-R media are to be pre-grooved for use, which is well known to those skilled in the art. Timing markings along a pre-grooved spiral track contains a wobble signal. This wobble signal provides CD laser head servo tracking alignment and clocking information to control disc spin rate. The native wobble is present throughout the prerecorded CD-R disc media, including the prerecorded track in the Power Calibration Area (PCA) 320, the Program Memory Area (PMA) 330, lead-in 332, data programming 334, or lead out 336 areas. Alternately this invention uses the timing-code information in the post-recorded data area of the CD-R media.
The present invention uses several methods for sensing the angular position of rotating or spinning CD-R media to be utilized in a radial printing system.
In another embodiment, the present invention uses several methods to further condition, extrapolate and otherwise process the utility of angular position event sources, which are marginal, to enhance their suitability for radial printing. For example, in one exemplary configuration of the present invention, a phase lock loop (PLL) is used to stabilize and multiply the angular position event source generated from either a spindle motor pole Hall Effects sensors or an encoder reading a low-count codewheel. In another exemplary configuration of the present invention, several variations of a synthesized multiplier method are used to digitally enhance, synthesize or otherwise extrapolate angular position event sources suitable for radial printing.
The present invention makes use of these signals either directly on CD-R media, from the rotation spindle motor, or from an encoder coupled to the rotation spindle motor shaft, in unique methods to provide angular position information for radially printing a label on the top surface of the CD-R media while it spins.
These and other features and advantages of the invention will be presented in more detail below with reference to the associated drawings.
The invention, together with further advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings.
a is a diagrammatic representation of a grid test pattern according to various embodiments of the present invention.
b is a diagrammatic representation of a Synthesized Multiplier Method according to various embodiments of the present invention.
The present invention will now be described in detail with reference to a preferred embodiment thereof as illustrated in the accompanying drawings. In the following description, specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without using some of the implementation details set forth herein. It should also be understood that well known operations have not been described in detail in order to not unnecessarily obscure the present invention.
To determine the instantaneous angular velocity and rate of disc spin specifically for radial printing, the radial printing system synchronizes with the spinning disc media or the CD-R device control system. To do this, this invention uses signals from among the following: (1) the inherent pre-grooved wobble frequency signal in the unrecorded track of a new CD-R disc as read from the laser read head of a CD drive mechanism, (2) the timing-code information in the data track of an already recorded CD-R disc as read from the laser read head of a CD drive mechanism, (3) an entirely independent encoding pattern pre-placed during manufacturing directly on the inner hub or outer circumference edge of the CD-R media, or post-placed by recording (burning) a timing pattern onto the media by the drive and reading it back for print timing purposes; (4) the signals from the rotating spindle motor, such as the motor poles, or (5) an encoding pattern from a code wheel coupled to the shaft of the rotating spindle motor with an external encoder sensor.
An embodiment of the present invention may use the pre-groove spiral track 350 wobble frequency signal 340 illustrated in
The advantage of this method is to provide accurate angular print information without the need for additional components, such as an external encoder and code wheel, since it uses standard CD-R media for all timing information. For example, an all-in-one device to record discs and print labels on encoder-pattern-grating CD/DVD media may be designed for lower overall manufacturing cost or may allow a smaller size of the device, because an external encoder or grating is unnecessary.
In another embodiment of the present invention, similar to that already described, the same considerations are necessary for printing on CD-R media; however, the disc media may contain partially completed recording information. This is illustrated in
Data Pattern Spiraling Angular Position and Mark
In another embodiment of the present invention, a radial printing device comprising of a CD drive as the spinning component may be configured with firmware to cause special data patterns to be written and read from the disc 100 in a form of instantaneous angular position information 140.
In yet another embodiment of the present invention, illustrated in
A zero synchronization or index mark widely known to and used by those skilled in the art is included in the encoder pattern 110/120 to reset the count with each rotation. A benefit of this new method is that it re-synchronizes the label position on a CD-RW media when re-inserted. This method enables removing and later reinserting the media multiple times to include additional printed content to the top surface of the media, or in the case of rewritable media (CD-RW/DVD-RW) this would allow adding new printed label information as new data is rewritten to the media, without the need for recognizing a previously printed label pattern. For example, one application is adding new picture files to previously recorded CD-RW (rewritable) media; the original disc label was prepared and saved as a template; upon reinsertion, the user updates the label template adding extra label or identification to the CD and then prints it again with prefect registration. In summary, this embodiment of the present invention shows how to include an optical or diffraction grating pattern directly on blank circular media, negating the need to add an external encoder grating pattern and enabling the new technology to be able to re-synchronize the label position on a CD when re-inserted.
The Nature of Signals Used, Created, Calculated or Derived
The nature of signals used, created, calculated or derived for radial print purposes is discussed: Correct pen firing signals are needed for the accurate registration of ink droplets. This timing information (for correct pen firing) is dependent on the instantaneous position of the CD/DVD disc (or spindle motor which drives it). Knowledge of the disc position, or its first derivative which is speed of rotation, and or its second derivative which is acceleration (or deceleration) is necessary and sufficient to provide this timing information.
Any or all measurement techniques and methodologies which measure, detect or determine any or all of disc position, rotational speed or acceleration are claimed as various embodiments for the purposes of radial printing. Some examples of such timing signal sources are: a) native signals from the disc drive itself; b) external transducers and sensors such as optical gratings and encoders, strobes etc; c) required timing information contained as signals written on the disc itself and decoded.
If measuring speed or acceleration, then the constants of integration (to obtain position or speed as the case may be) can be termed either ‘fixed’ or ‘relative’ and are respectively ‘fixed systems’ and ‘relative systems’. Both are determinate. If, by way of example, we are measuring disc rotation speed, and the constant of integration is ‘fixed’, for example by affixing a specific physical timing mark (reference or index mark) on the circumference of the rotating mechanism or platter, then when detected, that specific location is always ‘fixed’. This mark, together with the speed information allows you to know absolute position everywhere, and allows for features such as being able to stop the disc, start it again and continue printing where you left off. (since this reference mark is both fixed and determinate)
If this fixed mark 910 is positioned on the CD/DVD 100 itself, then in this fixed system, the disc could be removed from the mechanism, and put back in a new position on the platter. However, because of the affixed physical mark, when detected, absolute position is again known everywhere exactly as before removal from the spindle mechanism and printing could be resumed where it left off.
The constant of integration may also be ‘relative’, meaning that an absolute positional or physical mark doesn't exist. In such a relative system, no external index or reference information exists. In this case, a reference or index mark is created, derived or calculated and is selected by the electronics (hardware and or software) from rotational speed dependent signals, and is arbitrary for a particular printing session. Rotary period index pulses 818 and encoder pulse output 912 are examples of several possible rotational speed dependent signals that may be produced and obtained from several sources such as the cd drive 810 or from external encoding means 130. This reference or index mark represents an arbitrary but determinate and real position on the rotating disc. In such an embodiment, positional information is again, accurately known relative to the arbitrary index mark while the disc is rotating, and is sufficient for printing and completing the disc. All other angular positions signals such as 818, 912 and others as per alternate embodiments are known and determinate having a fixed and or well defined relationship with respect to this index mark 862, 914 by way of example. If however printing is interrupted and the disc is stopped, then the arbitrary mark is lost and so is the associated positional information. As such, printing could not be resumed continuing from ‘where it was left off’.
By way of further example, the angular position 140 may be derived from normal signals present within a CD-R recording system. Referring to
In
There are other ways the reference angular position may be derived, calculated or formulated from the rotary index signal (e.g., rotary index pulses 818) and or other timing information (e.g., wobble 340 or data-code 410 signals) since there is a fixed relationship between the reference angular position, the rotary index pulses and the pulses 340/410 of the timing information that collectively occur within one revolution of the rotating media. As such, reference angular position can be dependent on the timing information. For instance, as per
Similarly, other angular positions may be synthesized and determined. The source signals (positional 818, timing 340/410 etc) as discussed, provides knowledge as to the total number of pulses (interpolated or not) for a rotation. Counting these pulses, referenced to the rotation index pulse 862 for example, determines any angular position on the disc with resolution limited by the total number of pulses within a rotation. Other calculations may be made such as considering the difference between counts (e.g. their corresponding angular positions) which defines other angular displacements. Various angular displacements and their corresponding angular positions and or their angular position pulses 884 are required as are determined by specific radial print mechanism designs.
The number of signal pulses 340/410 between rotary index period pulses cannot change significantly in order to accurately predict the scale factor 864. However, if the laser radial position 816 is repositioned differently from the current helical writing or reading track 350 by the CD-R system, a more gross correction is required to generate accurate angular position 140 for the radial printing system. In this case, the signal pulse counter 840 must be recalibrated by clearing and recounting until the count 832 is stable.
Once the scale factor 864 is computed, it is used in a self-resetting period counter 870 to count down the number of signals per angular position 140. When the count reaches zero, the next rotationally sequenced angular position has been reached, and a signal equivalent to the encoder pulse
An alternative embodiment may be configured to retrieve angular position 140 from an encoder pattern manufactured into the CD-R disc media for a radial printing system. This is an example of a fixed system. Referring to
Extrapolation or Translation Measurement Techniques
In another embodiment of the present invention, a device may be configured to translate the angular position information from a pulse-train frequency source that is natively unsuitable for direct use in radial printing, i.e., either too low or too high. For example, the pulse train frequency source may be from the Hall Effects sensors of the spindle motor poles, or they may be from a low-resolution codewheel and encoder, or from a high-precision diffraction grating and encoder. Such translation mechanisms may be in the form of electronic frequency dividers (e.g., counters) or phase lock loops (e.g., frequency multipliers), depending on nature of the source or measurement signals, which represent techniques for the direct conversion of frequency (e.g., speed measurements).
By empirical observation, the ability of the rotating disc to instantaneously change rotational speed (and therefore its predicted/actual position by mathematical integration) is limited due to the rotational inertia possessed by the spindle system (mass) and the limit of magnitude of any external rotational forces (torques both positive and negative) that can be applied to the system. It is another empirical observation that once a disc system is rotating, the instantaneous changes in rotational speed e.g. wow and flutter are relatively small for the time period of interest for radial printing. However, it is critical for radial printing that wow which are slower changes in rotation speed and flutter which are more instantaneous changes in rotation speed, are accurately measured and tracked which is a fundamental purpose of any embodiment described in the present invention. Given these observations, the limits and boundaries of these operating parameters will now be more fully detailed illustrating methods used to determine or measure the maximum number of measurement events needed in order to fully characterize the physical rotational system and extrapolate or translate these measurements into the required number of angular positions needed for a radial print engine.
It is well known by those in the art that constant RPM rotational systems exhibit wow and flutter effects, which are modulations or changes to the constant speed. Closed-loop motor control systems of all types essentially make periodic measurements of speed and apply periodic corrective torque to the motor. This sequence of events causes the motor to speed up and then over time, due to frictional inertia, slow down, during repeated rotation. The long-term speed up and slow down is known as wow. In comparison, flutter involves instantaneous speed changes which are of shorter duration, and are localized events usually as a result of slip or grab in the bearings and mechanical systems or by sharp application of torque pulses from the motor, etc. The frequencies exhibited by wow are inversely proportional to the mass of the rotating system. Indeed, the wow of a large industrial motor is less than a hertz. Systems of the size of record player turntable exhibit wow from a few hertz to a few tens of hertz. Considering the low mass of a CD/DVD system one can expect wow and flutter in the few tens of hertz.
By empirical and experimental observation to minimize distortion and to optimize printing results, the present invention uses a convenient rotation speed approximately 500 RPM or less for radial printing. A CD drive also spins at 500RPM, the controlled speed at approximately the 2× rotation speed setting. While optimal printing speeds may be slower, 500 RPM is an available speed native to the drive's spindle motor system. As an experiment, using a 5000 line physical grating of the encoder spinning substantially constant at 500 RPM produces a raw pulse train at approximately 40 kHz (encoder channels A or B output). A spectrum analysis of this signal shows a fundamental spectral line at approximately 8.3 Hz, which is also the rotational speed (e.g., 8.3 rotations per second.) Having the fundamental at the rotational frequency indicates that the greatest instantaneous change in rotational speed happens once per revolution. Indeed, this is confirmed by the motor control electronics providing correction torque once per revolution. Harmonics, which contain all wow and flutter information, are 40 db lower than the fundamental at 100 Hz with some residual spectra out to 150 Hz. There are no spectra after 150 Hz. If an analog waveform having frequency components no higher than 150 Hz is digitized then via Nyquist's Theorem, a minimum of 2×150=300 samples per second are required to adequately capture all the existing information, i.e. to characterize the rotational system. Clearly a carrier of 40 kHz or samples/second is well over (over 100 times over sampling) the minimum necessary for an adequate capture or characterization. Having such a dense or fine grating produces a superior signal-to-noise ratio and clearly resolves all such low frequency changes (150 Hz or less); however, substantially no new speed or positional information is yielded above the theoretical minimum sampling rate of 300 Hz. Thus the higher cost of for such a precision encoder system is less warranted. However, higher sampling rates than the minimum are very desirable in order to yield better signal to noise ratios. This is experimentally confirmed when testing with a lower-count, 408 lines-per-rotation grating, which at 500 RPM produces a 3 kHz pulse stream. Such a grating or code-wheel more than adequately resolves or recovers all the spectra characterizing the rotational system and yields a valid radial printing encoder pulse stream 110130912.
In contrast to frequency domain results described above, similar investigations in the time domain further support the minimal necessary pulses per revolution needed to characterize the encoder and or detection system to yield a valid radial printing pulse stream. Experimentally, a frequency modulating (FM) discriminator was built with center frequency at 40 kHz and used with the 5000 line grating encoder system. This device will accurately demodulate any frequency deviations (i.e., speed changes as detected by the precision encoder system) from the 40 kHz carrier. The discriminator may be set to different capture bandwidths. This is similar to using a tunable filter, allowing one to resolve structure in the detected amplitude vs. time waveform. Specifically, the instantaneous amplitude of the detected time-domain waveform represents the instantaneous frequency of the carrier (e.g., rotational speed) at any instant of time in the rotation (e.g., position). The observed waveform is monotonic and periodic, and shows clearly the wow and flutter of the rotational system. Since it is already known experimentally that there are practically no frequency components above a couple of hundred hertz, it is sufficient to set a 1 kHz bandwidth for the discriminator, knowing that there is substantially no structure or events occurring faster than this bandwidth limit. The detected waveform has a very high signal-to-noise ratio, and all structure seen are relatively slow compared with the 1 kHz sampling granularity of the discriminator's 1 kHz RC time constant. Clearly observed experimentally is the periodic 8.3 Hz=120 ms wow, which is the speed up and slow down per rotation of the CD spinning platter mechanism spinning at 500 rpm. Seen also are 40 ms (25 Hz) structure as well as 80 ms structure. With the discriminator set to lower bandwidths (e.g., approximately 800 Hz and 250 Hz) we still see the above-mentioned structure still clearly resolved.
Investigations via looking at the frequency spectra and time domain waveform of the precision encoder show that changes in rotational speed are represented by significant spectral components of the order of 100 Hz and less, or via time domain, that any speed change in the rotational system takes 10 ms or more to occur. All spectral components are found to be below 150 Hz fixing the fact that rotational speed changes need to take approximately 7 ms or more to occur. Therefore theoretically, speed or positional measurements taken significantly more often than this, yields substantially no more new information. In reality and by observation, however, to improve signal-to-noise ratios, stability and ultimately print quality, rotational measurement updates are made more often than this.
In an exemplary configuration, a phase lock loop (PPL), well know by those in the art, may be configured to translate the above described measurement events to be used for radial printing. The PLL is a system and device that lends itself superbly well in a number of cases as a solution to providing the higher number of pen firing pulses or angular position pulses 884 needed with respect to the fewer such as signal 818, 912 measurement event pulses available. As an accurate frequency multiplier or extrapolator, the PLL provides the extrapolated number of pulses needed between each slower measurement event that are frequency and phase coherent. A stable PLL system can provide on the order of 1000 extrapolated pulses for each input pulse. Referring to
Included in
Motor Control Pulses from the CD Drive as the PLL Reference Input
A desired goal is to reduce the cost of a radial printing system by using a lower-cost encoder and codewheel system. One approach may be to avoid using an additional external codewheel and encoder by instead using the motor speed detection pulses native to the CD spindle motor control system. One embodiment of this present invention may be configured to control the pen firing for radial printing by using a configuration with a PLL to generate the needed high number of pen firing pulses per rotation. The CD drive's motor servo system uses a number of Hall Effect sensors fixed in the circumference of the spindle motor, which produce a digital pulse when a motor pole sweeps across each, sequentially and respectively. Therefore the instantaneous frequency of the pulse train produced by the Hall Effect sensors directly represents the instantaneous motor (and CD) rotation speed. By way of example, in a typical drive, the summed Hall Effect sensors produce 18 pulses per rotation at the motor control IC's 3× pin designation output, such as with a Rohm BD6670 or similar IC. A further limitation is that some drives have spindle motor controllers with only six pulses per rotation available at the IC's 1× pin designation output pin. To obtain needed speed information update measurements per rotation, when comparing the limited pulse stream of just 18 or fewer pulses per rotation, with just one measurement event every 20 degrees of rotation, versus the precision 5000 count grating encoder, which provided a measurement event every 0.072 degrees, a challenge exists to obtain a reliably good radial print image, given this low number of measurement update pulses per rotation. However, such a low number of measurement updates per rotation may be used for radial printing since only very low frequency spectral components are involved in characterizing the rotation.
At 500 RPM, the 3× output of the motor control chip produces a very stable near 50% duty cycle periodic 150 Hz pulse train. Indeed, at this RPM, the rotational period is 120 ms and with 18 measurements per rotation, we see that they occur every approximately 6.7 ms, often enough to capture all possible speed changes in the rotational system as discussed above. With this 150 Hz signal as the reference frequency input to the PLL, and a value of N=1024 for the N divider in the PLL, an output frequency of approximately 153.6 kHz was obtained, (150 pulses/sec×N), which is a pen firing pulse rate of 18,432 pulses/rotation (18×1024=18,432). An auxiliary divider 1160 (
Experimental results yield satisfactory results in printed output by a radial printer using a CD drive spindle motor with motor pole sensors and this PLL method. Close examination of the radial printer's output using a grid test pattern (see
When using an analog-digital PLL (DPLL), a configuration should adhere to the rule of having the filter cut-off frequency be of the order of 10 times lower than the carrier or input frequency. In this case the input frequency needs to be increased to an order of 1.5 kHz or more. Therefore for our analog-filtered PLL, a desirable way to get this higher input frequency is to increase the number of counts per rotation at a given rpm, by using an inexpensive codewheel or grating in lieu of having specialty spindle motors made having more Hall sensors. An important principle of this analysis is that if the analog PLL system did not have this restriction of seeking a factor 10 times the bandwidth equal to the reference frequency, and could recover all of the 150 Hz bandwidth, then the radial test print output grid pattern should yield totally straight lines 1204. Given this case, the 18 measurements per rotation (i.e., every 20 degrees of rotation) would be adequate for radial printing. In using an all-digital PLL (ADPLL) such as the TI 741s297, the above noted restriction with analog filters (DPLL) does not apply, so potentially greater recovered bandwidths are yielded.
Pre-Processing of Source or PLL Reference Signal
In an alternate embodiment, the angular position information 140 stream may be configured using the 1× or 3× motor control pulses or a low-precision codewheel such that the output signal and is pre-processed before conditioning by a PLL. Pre-processing of the source signal consists of first multiplying the source signal frequency up using non-PLL techniques, so that the source signal injected into the PLL is at higher frequency by some small factor, such as two or four times. For example one method for a configuration using the motor pole Hall Effect signals, the 150 Hz signal can be multiplied by 2 to 300 Hz by detecting the rising and falling transitions of the 150 Hz signal thereby doubling the number of measurement events, by using two monostables which are edge detection devices and then XOR'ing their outputs to get twice the frequency. In another configuration, circuits to detect edge transitions and to program appropriate delays may be used to construct the doubled frequency output. Encoder signal outputs, such as for use with codewheels, may have quadrature outputs, which when XOR'ed yield a frequency two times that of either of the two input channels; or when the quadrature outputs each combined with both positive and negative edge detection, signals which are four times the frequency of either of the two input channels are constructed. Alternatively, any other such pre-processing may be used to synthesize or extrapolate to higher frequencies before injection into the PLL. Improved print results may be achieved using techniques, such as just described, that allow recovery of a wider bandwidth as afforded by pre-processing the motor control signal. Such preprocessing is applicable to any source or input signal 1130 prior to conditioning by a PLL. Other PLL types, such as the All Digital PLL (ADPPL) like the TI 741s297 PLL, also may be used with the angular position information pulse stream with or without pre-conditioning.
Other techniques or implementations for obtaining higher frequency motor control pulses may be as follows: Setting up more Hall sensors in the circumference of the motor and having a combined output from summing each individual Hall sensor signal. In typical CD drives with 18 pulses for each rotation of the spindle motor shaft (the 3× signal), one configuration could improve performance by increasing the number of pulses per rotation by doubling or tripling or more for example, the number of Hall sensors installed in the spindle motor, at respectively decreasing angular spacing. Careful positioning at manufacture to insure that each Hall element is equidistant from its neighbor will insure a best possible desired 50% output duty cycle waveform. Such may be necessary if radial printing is done at significantly lower speeds than 500 RPM, since at lower spin-rate speeds the rotational inertia is lower with an inherently less stable drive platform, resulting in more wow and flutter errors. In this case far more measurements than once every 20degrees are necessary to adequately track rotation speed changes.
Another embodiment of the present invention may use a method of the above that would increase the output frequency of the encoder or motor pole—Hall sensor source. The method is similar to that of an optical grating technique, where a second physical set of Hall Effect sensors in a concentric ring, identical to the first set, is configured such that it is affixed at a 90-degree rotational offset, such that the 2concentric rings of sensors are physically offset with respect to each other by 90degrees. The second ring of sensors thus produces an output frequency identical to the first ring but at 90 degrees out of phase creating a quadrature signal with respect to the first. The two resultant pulse streams may be combined electronically in quadrature to yield a 2× and or a 4× frequency output.
Synthesized Multiplier Methods SMM
Yet another embodiment of the present invention may be configured to use a synthesized multiplier method or “SMM” as abbreviated and used herein. In this configuration for detection 1200, the encoder's square wave signal 1210 is used to open and close a gate passing a high speed clock signal 1220 to a counter. The number of pulses that the counter counts 1230 is directly proportional to the signal pulse width, hence its instantaneous frequency. The number of pulses ‘captured’within each pulse width of the incoming pulse train represents information relating to the instantaneous frequency and frequency changes of the incoming pulse train, which again is directly related to instantaneous motor speed and disc position. This information may be directly operated on or may be coded as mnemonics 1308 which may be used to synthesize or control a pulse train at some desired output frequency. Real-time processing may be needed to create a synthesized pulse train whose frequency changes are constructed directly from this captured information. Even though this method may be useful in the preprocessing block, it may also be used to replace the PLL, again where mnemonics representing encoder information 1310, 1320 are used to control a synthesized pulse train, which then is the pen-firing signal.
The several embodiments and methods described above are applicable to any type of physical detection mechanism. In other words any detection mechanism may be used to obtain the angular position necessary for radial printing. For example, the detection system may be configured to use magnetic means as in the case of motor poles brushing past Hall sensors, or it could be an optical detection mechanism where light is passed through or reflected from an optical grating to produces signals that contain information on rotation speed or position. To clarify, having more Hall sensors positioned closer together in the spindle motor's stator is equivalent to having a finer optical grating, all of which equates to having more updating or detection events occur per rotation. Having two rings of Hall sensors positioned in quadrature is the same as having two optical sensors positioned in quadrature thereby generating two pulse streams 90 degrees out of phase with respect to each other.
Synthesized Multiplier Methods
Synthesized Multiplier Methods (“SMM” as used herein) may be used in an embodiment of the present invention to represent indirect frequency multiplication or translation methods. In general, such methods and techniques digitally capture the measurement information and in turn, using different mathematical or algorithmic procedures, operate on the captured measurement information and process it. For example, a radial printing system may be configured to use methods to convert and translate the annular measurement information to other operators that control a fast clock to create or synthesize representative high frequency signals (e.g., multiplication), which in turn yields the required pen timing signals providing the required number of pulses or counts per disc rotation for use in radial printing. These conversion techniques, whether direct or indirect, are not restricted to linear mappings, such as input frequency to output frequency. Various interpolations may be preformed, linear or otherwise, to tailor the printhead pen firing timing signal either for general radial print quality improvements, or for corrections due to various biases, interference patterns, etc.
The Synthesized Multiplier Method (SMM) will now be explained in more detail. As has been previously described, the varying pulse widths of the encoder signal represent instantaneous frequency changes, therefore CD disc speed and positional changes. Quantifying each pulse width in the encoder train can easily be done as discussed. Using the rising edge of a pulse to open a gate and its falling edge to close the gate which passes a stream of high speed system clock signals is a simple detection method which relates the pulse width to the number of clock pulses counted. Each detection count is assigned a “bin” which is a memory location. The number of bins determines the control or resolution of the output frequency synthesizer. The number of bins is equal to the number of measurement events per rotation. One may note that the accuracy of determining a pulse width will be +/−2 clock counts 1302 (one when the gate opens and one when it closes), the degree of accuracy as a percentage of total counts per width is determined simply by the choice of clock frequency 1302, where the higher frequency may yield more accurate measurements. A reasonable limit at which accuracy no more serves the precision of the measurement is determined by “noise” and “flutter,” inherent as instabilities of the rotational system. By way of example, there are uncertainties in the motor pole system, of actually when the Hall Effect sensor fires and releases, thus introducing uncertainty or jitter into the system. Each pulse width therefore will tend to have some random error associated with it.
SMM—General
In one embodiment of the present invention, a first approach (SMM1) uses no averaging, is done in real time meaning that there is essentially no delay from input to output signals and can use simple filtering or processing, such as smoothing. Memory locations called “bins” are constructed. Each bin is assigned an upper 1404 bound and lower 1402 bound for the detected count value 1304. The size of each bin is determined by the difference between its upper and lower bound. Each detected count value will therefore find itself a bin. Each bin 1400 has an associated mnemonic 1308 or code or value assignment which when mathematically operated on produces control data 1310, which is used to control a high frequency clock (either the same one 1302 or other equivalent) to synthesize the correct output pen-firing signal. Specifically: f(x)=x′. Here x′ 1310 is the mnemonic or code associated with value x 1304 within bin x. When operated on 1308, the result is x′ 1310 which is a value associated with the control data which controls the high speed clock 1302 producing the generated or synthesized output frequency 1306. Similarly, f(y)=y′ where y′ is the mnemonic associated with bin y. When bin y is operated on 1312, the result is y′1320 which is associated with the control data that produces the output frequency 1314. Again, a fast clock (synchronous) 1302 is used as the basis for constructing or synthesizing the output (pen) signal. Each mnemonic instructs/determines how many of these fast clock pulses should be assigned “high” (with an equivalent number for “low” to produce a 50% duty cycle). In other words, each mnemonic 1308, 1312 is associated with a different frequency 13061314. The more the bins, the more discrete frequencies are synthesized. For the duration of time that any one bin is active, it is its associated frequency that is produced 1306, which is a continuous pulse train of the same-sized highs and lows which is at a specific frequency. Only one bin may be active at any one time. When another bin and its associated mnemonic and control data become active, there is a step function change 1310 to a new discrete frequency 1314. This new bin and mnemonic represents new information determining a new number of how many fast clock pulses stay high and equivalently low. Each bin stays active for one cycle or period of input or encoder frequency. With this system, the output (pen) signal 1330 is composed of a stream of different discrete frequencies, whose frequency at any time is determined by the active bin. The transition event 1310 occurs when another bin becomes active.
SMM1—Detailed
Describing this approach above in more detail, for another embodiment of the present invention, the active bin is the one that is being currently filled or chosen; for example, by the detected count value that selected it. This approach may be similar or equivalent to the sample and hold method described above used in the analog PLL filter. The difference being that in the analog PLL system there is an RC time constant that smoothes the transition to a new frequency, where as in the simple SMM approach system there is no time constant smoothing the discrete transitions, not normally an issue if the discrete jumps are small. Where there is an issue with this approach is that exactly what is detected (and therefore its associated mnemonic) is what is generated in the output signal to the pen. So for example, if an excessive jitter, or noise such as a spike or some other anomalous effect occurs for some particular period of the encoder input, then that anomaly is instead output. Thus instead of a completely orderly increment or decrement in bin numbers, the result is bin numbers jumping randomly or haphazardly among positions, even though following a general trend of increasing or decreasing frequency. The orderly increase and decrease in bin numbers may be well obscured even though present due to monotonic trend. In other words, the regular monotonically increasing or decreasing frequency changes which accurately characterize the rotation pattern can be sharply broken due to noise or other measurement anomalies.
[SMM1a]
For yet another embodiment of the present invention, some simple smoothing may be possible for the SMM1 system previously described in order to contour and force a more orderly behavior, such as with filtering. This alternative configuration will be called “SMM1a” as used herein. SMM1a is an extension of SMM1 with additional filtering or smoothing introduced. Filtering is based on introducing a software rule that “limits how far away” the next active bin can be compared to the current active bin. The rule defines and limits how many bins that may be skipped over to find the next active one. In other words, where noise spikes or other measurement anomalies may cause a “far away” bin number to become active, a rule may be set up limiting how far the excursion can be. In referring to
[SMM2: Pseudo Real Time Smoothing (via Sampling and Accumulation)]
Another embodiment of the present invention, may be configured to use pseudo measurement-time smoothing via sampling and accumulation, and will be called “SMM2” as used herein. Each rotational system is in fact slightly different than its same manufactured-lot numbered sibling, and even more slightly different than its cousin from another lot. It would be desirable to characterize each drive's spindle motor individually. This can be done, since it is observed that the pattern of speed changes is constant and repetitive within each rotation and from rotation to rotation in each given drive. Identifying this pattern goes hand in hand with controlling the noise or random fluctuations. The following algorithm method is used for the SMM2 method:
(A) As per
(B) One allows several rotations to occur at the steady state rotation speed. The first rotation fills memory location 1 in each of the 18 slots. (s1m1, s2m1, . . . s18m1). The next rotation (rotation #2) fills memory location 2 in each of the 18slots (s1m2, s2m2, . . . s18m2) and so on. With each succeeding rotation, new entries (detection counts) are accumulated or stored within the several memory locations associated with each slot. The final or actual value (and mnemonic) for each slot is the average of its several entries.
C) Several averaging or weighting schemes are possible, either with or without weighting. The simplest scheme would be the running average, where the number of entries to be averaged remains some fixed constant. For example if the constant was 5, then 5 rotations would have to go by. The 5 entries (for that slot) would be averaged, and the result would be the detection value (and mnemonic) for that slot. For the next or 6th rotation, the first rotation's detected value entry would be discarded, the 6th's rotation's detected value entered and the 5 values once again are averaged producing the new detection value for that slot. As soon as that averaging calculation is made, that detection values mnemonic is used to control the pen output generator. Each slot's detection value is mathematically operated upon (at the least, simply scaled by a constant) that will control or cause the synthesized output to produce the correct frequency (defined) for the time the slot is active. Thus the slot's newly averaged values (after being operated on—mnemonic) determine the actual output frequencies as the slots are stepped though in sequence. The number of slots determines the granularity or size of each frequency step-the fewer the number of slots, the larger the steps.
Greater averaging yields more filtering or noise reduction. Signal-to-noise or smoothing scales as the root of the number of averages made. Other averaging schemes may be alternatively possible, such as taking the current average value (detection value) and adding it to the newest or latest measurement detected value and dividing by two to create the new average detection value. Weighting coefficients to the two terms may be used in order to select more or less emphasis on past versus latest entries. Similarly, a more general case may apply a weighting coefficient to each term in the average.
[SMM3→SMM2 Plus Interpolation.]
Another embodiment of the present invention, may be configured to use pseudo measurement-time smoothing via sampling and accumulation plus interpolation, and will be called “SMM3” as used herein. A radial printing system may be configured using motor poles and as such may have a number of measurement slots. For example, a typical CD drive spindle motor system produces 18 pulses per rotation. Each of these 18 pulses per rotation is a measurement event, with the results of each measurement or measurement value stored in each of the 18 successive slots. In
For example, if the number of pseudo slots is made equal to the number of dm slots (
[SMM4: Fourth Approach SMM: Using ‘Sigma-Delta’ Techniques]
Yet another embodiment of the present invention may be configured to use Sigma-Delta techniques and will be called “SMM4” as used herein. In the digitization of analog waveforms, widely known in the art, codec's may use sigma-delta encoding methods. Essentially, a digital word which represents the amplitude value of the input waveform when sampled, and is subtracted from the previously sampled word. These differences are what are stored or remembered, and then are later used to reconstruct the waveform. In the present embodiment, this approach may be used as a variant of SMM3 method previously described, wherein values created for interpolated pseudo slots are obtained by operating on the differences between measurement slots. For example,
In the example above, equal weighting may be given to each pseudo slots detection value using the same increment. This method is appropriate when the number of pseudo slots created is relatively small or if the rate of change in disc speed is constant between measurement slots. However, if many pseudo slots are to be created between measurement slots, then different weightings should be made for each increment used. Such weightings will assign more correct detection values to the pseudo slots reflecting actual speed changes. This is especially important where the sign of the slope of the speed changes between two far-apart measurement slots. Pseudo slots can be assigned values based on the calculated increment or may be modified depending on the acceleration or deceleration behavior of the speed changes. The objective is to tailor the detection values and associated mnemonics so as to follow or duplicate the waveform typified at a DPLL's VCO control line 1170 or other detector showing speed changes vs. time. Methods SMM2 to SMM4 as previously described above are based upon the fact that the behavior of the rotating system is consistent and repeatable, rotation after rotation. The rotational system's inertia together with applied torque via servo system control, defines monotonically increasing and decreasing speed changes, which are consistent and repeatable rotation after successive rotation. Experimental results have shown this to be the case. Where servo systems are not used to control the motor speed, we again observe consistent, repeatable patterns representing speed changes within each rotation and from rotation to rotation. Where this is the case, methods SMM1 to SMM4 may be applicable.
The exemplary concept and novel use of signal processing to determine angular position information for radial printing as defined in the present invention illustrate the overall principle and application of the more general solution for a highly integrated system for recording and label printing circular media in a single insertion of the media. While this invention has been described in terms of several preferred embodiments, there are alterations, permutations, and equivalents that are all within the scope of this invention. For example, these techniques equally apply to radial sled printing as disclosed in co-pending U.S. Provisional Patent Application No. 60/566,468, filed Apr. 28, 2004, which is hereby incorporated by reference. It is therefore intended that the following appended claims be interpreted as including all such alterations, permutation, and equivalents as they fall within the true spirit and scope of the present invention.
This application is a continuation-in-part of U.S. application Ser. No. 09/815,064, filed Mar. 21, 2001, now U.S. Pat. No. 6,736,475, which claims the benefit of U.S. Provisional Application No. 60/191,317, filed Mar. 21, 2000, wherein these references are hereby incorporated by reference in their entirety for all purposes. This application is also related to U.S. application Ser. No. 09/062,300, filed Apr. 17, 1998, now U.S. Pat. No. 6,264,295, which is also incorporated herein by reference in its entirety for all purposes.
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| Number | Date | Country | |
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| Number | Date | Country | |
|---|---|---|---|
| Parent | 09815064 | Mar 2001 | US |
| Child | 10848537 | US |
