Abstract:
A scanner self-adaptive to an optimized scanning speed, comprising: a register storing a scanning speed parameter; a frequency adjusting circuit outputting a driving signal having variable frequency corresponding to the scanning speed parameter using a predetermined method; and a stepping motor controlling the scanning speed of the scanner, coupled to receive the driving signal and changing its rotate speed, as well as the scanning speed of the scanner, corresponding to the frequency of the driving signal.

Description:
BACKGROUND  
       [0001]     The invention is related to a scanner, and more particularly, to a scanner with optimized self-adaptive scanning speed.  
         [0002]     Stepping motors are typically used in scanners to drive scanning heads.  
         [0003]     Carriage jams are a kind of problem typically occurring in scanners. A carriage jam occurs when stepping motor stops rotating due to the environment working against the torque generated by the stepping motor, when the stepping motor receives an active driving signal. To prevent carriage jam, some considerations must be taken into account when designing the scanners.  
         [0004]     First, the effective life of a typical scanner is about 8 years and 100,000 scans. To ensure that all scanners can reach the requirement, stepping motor speed is typically hold to 70% of the maximum specification. Second, the voltage level tolerance of the power adapter the scanner connected thereto is typically held to about ±5%. The load a stepping motor carriage can bear has about ±5% tolerance. To meet the tolerance mentioned above, the stepping motor speed is held to 90%. Third, for the scanner to function at 5˜45° C., the speed of stepping motors is further reduced by 5% off for the worst case scenario. Fourth; the speed specification of the stepping motor should be reduced another ±5%, to ensure the scanner operation at various angles, even vertical. To ensure the designed scanning speed is applicable to scanners of the same model, the speed specification of the stepping motor should be reduced by about 50%.  
         [0005]     Additionally, the scanning quality of the scanner is proportional to the number of illuminations per scanning cycle. The scanning duration can be reduced using a higher scanning speed, while the scanning quality can be better using a lower scanning speed. If the scanner can scan at only one speed, scanning speed cannot be altered to fulfill individual requirements.  
         [0006]      FIG. 1  is a block diagram of a conventional scanner  10 . A frequency divider  12  receives an oscillating signal F c  with a static frequency generated by an oscillator  11 , and outputs a driving signal D m  by dividing the frequency of the oscillating signal F c  to a stepping motor  13 .  
         [0007]     The frequency divider  12  uses a static ratio to divide the oscillating signal F c . As soon as the specification of the oscillator  11  is determined, the speed of the stepping motor is set and the scanning speed of the scanner is then fixed. There is no easy way to adjust the scanning speed to adapt to the current condition of the scanner. Scanners with the same specifications must shares the same scanning speed, which is determined to operate under the worst case scenario of all required operational specification.  
       SUMMARY  
       [0008]     The present invention relates to a drive circuit for a scanner that obviates one or more of the problems due to limitations and disadvantages of the related art.  
         [0009]     Consistent with the present invention, there is provided a scanner self-adaptive to an optimized scanning speed, comprising: a register storing a scanning speed parameter; a frequency adjusting circuit outputting a driving signal having variable frequency corresponding to the scanning speed parameter using a predetermined method; and a stepping motor controlling the scanning speed of the scanner, coupled to receive the driving signal and change the rotational speed thereof, as well as the scanning speed of the scanner, corresponding to the frequency of the driving signal.  
         [0010]     Consistent with the present invention, there is provided a scanner self-adaptive to an optimized scanning speed, further comprising a carriage jam detector which deducts the scanning speed parameter value stored in the register, when a carriage jam of the scanner is detected by the carriage jam detector.  
         [0011]     Additional features and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The features and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.  
         [0012]     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0013]     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and together with the description, serve to explain the principles of the invention.  
         [0014]      FIG. 1  is a block diagram of a conventional scanner  10 .  
         [0015]      FIG. 2  is a block diagram of a scanner  20  consistent with the first embodiment of the invention.  
         [0016]      FIG. 3  is a block diagram of a scanner  30  consistent with the second embodiment of the invention.  
         [0017]      FIG. 4  is a block diagram of a scanner  40  consistent with the third embodiment of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0018]      FIG. 2  is a block diagram of a scanner  20  consistent with the first embodiment of the invention. The scanner  20  includes a register  22  storing a scanning speed parameter. A frequency adjusting circuit  21  outputs a driving signal D m  with programmable frequency corresponding to the scanning speed parameter. A stepping motor  23  controlling the scanning speed of the scanner  20  is coupled to receive the driving signal D m . The rotational speed of the stepping motor  23  corresponds to the frequency of the driving signal D m , and therefore changes the scanning speed of the scanner  20 .  
         [0019]      FIG. 2  also shows an example of an implementation of the frequency adjusting circuit  21 . The frequency adjusting circuit  21  comprises a pulse width modulation (PWM) device  211 , a filter  212 , a voltage controlled oscillator and a voltage divider  214 .  
         [0020]     The PWM device  211  outputs a voltage adjusting signal F r . The voltage adjusting signal F r  is a square waveform whose duty cycle corresponds to the scanning speed parameter stored in the register  22 .  
         [0021]     The filter  212  is coupled to receive the voltage adjusting signal F r . The filter  212  filters the voltage adjusting signal F r  and outputs a DC power V 1  whose voltage corresponds to the duty cycle of the voltage adjusting signal F r . The filter  212  can be a simple resistor-capacitor (RC) filter or other filter. The DC power V 1  has a higher level when the duty cycle has a higher value. The PWM device  211  working with the filter  212  is a typical implementation of a DC-DC power converter, sometimes named a switching power regulator. The DC power output level corresponds to the scanning speed parameter stored in the register  22 .  
         [0022]     A voltage controlled oscillator  213  is coupled to receive the DC power V 1  and outputs an oscillating signal F c , whose frequency corresponds to the voltage of the DC power V 1  as determined by the voltage controlled oscillator  213 .  
         [0023]     A frequency divider  214  coupled to receive the oscillating signal F c  outputs the driving signal D m  to the stepping motor  23  by dividing the frequency of the oscillating signal F c  in a predetermined ratio. The frequency of the driving signal D m  is thus adjusted by the changed scanning speed parameter stored in the register  22 .  
         [0024]     In this embodiment of the invention, the scanning speed of the scanner  20  can be changed by modifying the scanning speed parameter stored in the register  22 .  
         [0025]      FIG. 3  is a block diagram of a scanner  30  consistent with the second embodiment of the invention. The scanner  30  includes a register  32  storing a scanning speed parameter. A frequency adjusting circuit  31  outputs a driving signal D m  with programmable frequency corresponding to the scanning speed parameter. A stepping motor  23  controlling the scanning speed of the scanner  30  is coupled to receive the driving signal D m . The rotational speed of the stepping motor  33  is corresponding to the frequency of the driving signal D m , and therefore changes the scanning speed of the scanner  30 .  
         [0026]     The scanner  30  further comprises a carriage jam detector  35 . The carriage jam detector  35  deducts the scanning speed parameter value stored in the register  32 , when a carriage jam of the scanner is detected by the carriage jam detector  35 .  
         [0027]     The carriage jam detector  35  connects to a first located point sensor  351  and a second located point sensor  352 . The first located point sensor  351  generates a signal L 2  to inform the carriage jam detector  35  that the scanning head  34  is arriving or leaving a first located point. The second located point sensor  352  generates a signal L 1  to inform the carriage jam detector  35  the scanning head  34  is arriving or leaving a second located point. The carriage jam detector  35  can then determine the scanning speed, as a first time length, by calculating the time required for the scanning head  34  to travel from the first located point to the second located point, or the time required for the scanning head  34  to travel from the second located point to the first located point. The carriage jam detector  35  then compares the first time length with a reference time length corresponding to the current scanning speed for determining if any carriage jams have occurred. The reference time length is the time required for the scanning head  34  to travel from the first located point to the second located point or from the second located point to the first located point using the same scanning speed. The reference time length can be found by providing a reference scanner which can run without carriage jam in a reference environment, with scanning speed thereof set to any value at which the current model might run. By calculating the time required for the scanning head  34  of a reference scanner to travel from the first located point to the second located point or from the second located point to the first located point at the varied speeds, a table storing reference time lengths at different scanning speeds is recorded in the system controlling the scanner. The carriage jam detector  35  can then access the reference time length according to the current scanning speed from the system.  
         [0028]      FIG. 4  is a block diagram of a scanner  40  consistent with the third embodiment of the invention. The scanner  40  includes a register  42  storing a scanning speed parameter. A frequency adjusting circuit  41  outputs a driving signal D m  with programmable frequency corresponding to the scanning speed parameter. A stepping motor  43  controlling the scanning speed of the scanner  40  is coupled to receive the driving signal D m . The rotational speed of the stepping motor  43  corresponds to the frequency of the driving signal D m , and therefore changes the scanning speed of the scanner  40 .  
         [0029]     The scanner  40  further comprises a carriage jam detector  45 . The carriage jam detector  45  deducts the scanning speed parameter value stored in the register  42 , when a carriage jam of the scanner is detected by the carriage jam detector  45 .  
         [0030]     The carriage jam detector  45  connects to an induced output terminal F B  of the stepping motor  43 . When the stepping motor  43  receives an active driving signal D m , the magnet inside the stepping motor changes its position and therefore the magnetic flux field inside the stepping motor is changed. The coil of the induced output terminal F B  induces the magnetic flux change and generates a first waveform. A waveform comparator inside the carriage jam detector  45  compares the first waveform with a reference waveform to determine if a carriage jam has occurred. The reference waveform is the waveform output from an induced output terminal of the stepping motor  43  without carriage jams, which can be measured from a reference scanner working in a reference environment.  
         [0031]     By using the embodiments consistent with the invention, there is no need to determine a specified scanning speed for the same scanner models. Users can program a scanner to work at the scanning speed they prefer regardless of the condition and the environment the scanner is used. Users can also program the scanner to scan at lower speeds if they wish to achieve better scanning quality. Therefore, the scanners can adapt to an optimized scanning speed, thus fulfilling the personal or environmental requirements.  
         [0032]     While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. Those who are skilled in this technology can still make various alterations and modifications without departing from the scope and spirit of this invention. Therefore, the scope of the present invention shall be defined and protected by the following claims and their equivalents.