Abstract:
The present invention provides an over drive power control system and a method which are capable of generating an optimized output power of the optical disk drive under a variation of operational environment. According to this invention, a photo detecting unit detects current laser power and generates a power feedback signal. A low frequency power control unit generates a modified power control signal by using the power feedback signal and an original power control signal. A high frequency power control unit generates a modified high frequency control signal for controlling the laser power according to a predetermined relationship among original and modified low power control signals and an original high frequency control signal. A digital-to-analog converter receives the modified high frequency control signal then outputs a adjusted write power signal for adapting the laser power to environmental variation and thus maintaining laser power in a constant state.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention generally relates to a power control system and a method of same for controlling an optical disk drive, which are capable of generating an optimized output power of the optical disk drive under a variation of operational environment. 
       BACKGROUND OF THE INVENTION 
       [0002]    In power control of an optical disk drive during a high-speed recording procedure, a power waveform of single level often causes a bad formation of the pits (or marks) on a recordable disk. As a result, conventional optical disk drive introduces a power control of composite waveform for increasing the writing performance, such as an over-drive power control to a CD-R media or a multi-pulse power control to a CD-RW media. 
         [0003]    The main power of the laser generated by a laser diode of the optical disk drive is controlled by a write power control unit, for example. The write power of the laser is detected by a photodetector and then sampled by a sample and hold device according to a main power sample hold pulse. The sampled write power signal is fed back to the write power control unit as a feedback power signal. Then the write power control unit can adjust the write power of the laser using the feedback power signal. The above operations are similar to the read power. However, for an over drive power or multipulse power signal of the laser, the sampled period is very short Hence, the sampled feedback signal will be incorrect if the sampling bandwidth of the laser power feedback signal is not sufficient to support such short sampled period power signals. Further, the laser power control will be inconstant or incorrect if a high-frequency noise is induced. 
         [0004]    As mentioned, since the sampled period of the over-drive power signal or the multi-pulse power signal are much shorter than that of the writing pulse or reading pulse, a higher bandwidth of the feedback signal of laser power and power control circuit is required, especially in a high-speed recording condition. Consequently and undoubtedly, the higher bandwidth induces a higher cost. 
         [0005]    Some conventional arts adopt an open DAC (Digital to Analog Converter) control instead of the APC methods of the over-drive power control or the multi-pulse power control. The open DAC control means to control the OD power or the multipulse power at a constant level. Nevertheless, the optimized write power cannot be achieved by the open DAC control when the characteristic of laser diode varies under variation of operation environment, such as operation temperature. Therefore, the recording performance of the optical disk drive by open DAC control will be degraded under a varied operation environment. 
         [0006]      FIG. 1  illustrates a diagram of characteristic relationship lines of the reading DAC value relative to the read power at specific temperatures. Referring to the left line in  FIG. 1 , a first read power rPW 1  is achieved while the reading DAC value is of a first reading DAC value rDAC 1 . Similarly, a second read power rPW 2  is relative to a second reading DAC value rDAC 2 . The DAC value is related to a gain of the digital-to-analog converter. Basically, the read powers are directly proportional to the reading DAC values, i.e. the read powers are ascendant while the reading DAC values increase. It should be noted that the characteristic relationship of a writing DAC value relative to the write power is similar to which of the reading DAC value relative to the read power. 
         [0007]    As shown, relationships of the DAC value relative to the laser power at different temperatures are different. It is obvious that the two characteristic relationship lines have different slopes under different temperatures, i.e. the relationship of the DAC value relative to laser power would be varied with the temperature variation. The optical disk drive can adjust the laser power by determining a proper DAC value in accordance with the different characteristic relationships which are stored in the memory. 
         [0008]    The characteristic relationship of the DAC value relative to the laser power can be explained clearly by following equations with detailed explanation. Referring to  FIG. 1  again, we can set two reference reading DAC values rDAC 1  and rDAC 2  under a specific temperature for obtaining two corresponding read power rPw 1  and rPw 2  respectively. Thus, the equation (1) is obtained to represent the characteristic relationship of DAC value relative to laser power. 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       Δ 
                        
                       
                           
                       
                        
                       rDAC 
                     
                     
                       Δ 
                        
                       
                           
                       
                        
                       rP 
                     
                   
                   = 
                   
                     
                       
                         rDAC 
                          
                         
                             
                         
                          
                         2 
                       
                       - 
                       
                         rDAC 
                          
                         
                             
                         
                          
                         1 
                       
                     
                     
                       
                         rPw 
                          
                         
                             
                         
                          
                         2 
                       
                       - 
                       
                         rPw 
                          
                         
                             
                         
                          
                         1 
                       
                     
                   
                 
               
               
                 
                   ( 
                   1 
                   ) 
                 
               
             
           
         
       
     
         [0000]    wherein rDAC represents a reading DAC value of the digital to analog converter, ΔrDAC represents a reading DAC variation of the digital to analog converter, and ΔrP represents a read power variation of the laser emitting unit. 
         [0009]    Then, we can derive the proper reading DAC value rDAC from equation (2). 
         [0000]    
       
         
           
             
               
                 
                   rDAC 
                   = 
                   
                     
                       
                         
                           Δ 
                            
                           
                               
                           
                            
                           rDAC 
                         
                         
                           Δ 
                            
                           
                               
                           
                            
                           rP 
                         
                       
                       × 
                       rPw 
                     
                     + 
                     rOffset 
                   
                 
               
               
                 
                   ( 
                   2 
                   ) 
                 
               
             
           
         
       
     
         [0000]    wherein rPw represents a current read power, rOffset represents a read power offset of the laser emitting unit. 
         [0010]    Similarly, the writing DAC value can be derived from the equations (3) and (4). 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       Δ 
                        
                       
                           
                       
                        
                       wDAC 
                     
                     
                       Δ 
                        
                       
                           
                       
                        
                       wP 
                     
                   
                   = 
                   
                     
                       
                         wDAC 
                          
                         
                             
                         
                          
                         2 
                       
                       - 
                       
                         wDAC 
                          
                         
                             
                         
                          
                         1 
                       
                     
                     
                       
                         wPw 
                          
                         
                             
                         
                          
                         2 
                       
                       - 
                       
                         wPw 
                          
                         
                             
                         
                          
                         1 
                       
                     
                   
                 
               
               
                 
                   ( 
                   3 
                   ) 
                 
               
             
             
               
                 
                   wDAC 
                   = 
                   
                     
                       
                         
                           Δ 
                            
                           
                               
                           
                            
                           wDAC 
                         
                         
                           Δ 
                            
                           
                               
                           
                            
                           wp 
                         
                       
                       × 
                       wPw 
                     
                     + 
                     wOffset 
                   
                 
               
               
                 
                   ( 
                   4 
                   ) 
                 
               
             
           
         
       
     
         [0000]    wherein wDAC 1  and wDAC 2  represent two reference reading DAC values with respect to two write power wPw 1  and wPw 2  respectively under a specific temperature, ΔwDAC represents a writing DAC variation of the digital to analog converter, ΔwP represents a write power variation of the laser emitting unit, wPw represents a current write power, wOffset represents a write power offsets of the laser emitting unit, wDAC represents a proper writing DAC value of the digital to analog converter. 
         [0011]    Further, we can also obtain two output voltage signals VO 1  and VO 2  of a reading channel of the APC circuit, with respect to the read powers rPw 1  and rPw 2  respectively. Accordingly, the characteristic relationship of the output voltage signal relative to the read power can be explained by the equation (5). 
         [0000]    
       
         
           
             
               
                 
                   
                     
                       Δ 
                        
                       
                           
                       
                        
                       P 
                     
                     
                       Δ 
                        
                       
                           
                       
                        
                       V 
                     
                   
                   = 
                   
                     
                       
                         rPw 
                          
                         
                             
                         
                          
                         2 
                       
                       - 
                       
                         rPw 
                          
                         
                             
                         
                          
                         1 
                       
                     
                     
                       
                         VO 
                          
                         
                             
                         
                          
                         2 
                       
                       - 
                       
                         VO 
                          
                         
                             
                         
                          
                         1 
                       
                     
                   
                 
               
               
                 
                   ( 
                   5 
                   ) 
                 
               
             
           
         
       
     
         [0000]    wherein the value of ΔP/ΔV represents a variation parameter of output power to output voltage of the APC circuit under different temperatures. 
         [0012]    We may assume that the output voltage signal of reading channel of the APC circuit is VRO 1  at a specific temperature. The characteristic of laser power will be varied by the variation of environment temperatures due to a temperature-rising environment or the high heat capacities produced during the recording operation of the optical dick drive. Therefore, the output voltage signal of APC circuit will be changed to VRO 2  in order to maintain a constant output of laser power. Accordingly, we can obtain the characteristic relationship of the variation of the read power due to the variation of temperatures by comprehending equation (5), shown as equation (6). 
         [0000]    
       
         
           
             
               
                 
                   
                     Δ 
                      
                     
                         
                     
                      
                     Pr 
                   
                   = 
                   
                     
                       ( 
                       
                         
                           VRO 
                            
                           
                               
                           
                            
                           2 
                         
                         - 
                         
                           VRO 
                            
                           
                               
                           
                            
                           1 
                         
                       
                       ) 
                     
                     × 
                     
                       
                         Δ 
                          
                         
                             
                         
                          
                         P 
                       
                       
                         Δ 
                          
                         
                             
                         
                          
                         V 
                       
                     
                   
                 
               
               
                 
                   ( 
                   6 
                   ) 
                 
               
             
           
         
       
     
         [0000]    wherein ΔPr represents the variation of read power of the laser emitting unit under the temperature variation. 
         [0013]    Although the varied temperatures can be detected by using a temperature sensor, the usage of the temperature sensor by aforementioned power control methods of laser power will increase the cost of the optical disk drive. Further, conventional control methods would be easily invited within incorrect sampling signals by using a high-speed APC circuit in a high-speed recording condition. Also, that will increase the manufacturing cost of the optical disk drive to raise the sampling rate of signals. 
       SUMMARY OF THE INVENTION 
       [0014]    According to the present invention, a power control system of an optical disk drive is provided to effectively and dynamically control over drive or multipulse power of the optical disk drive. The optical disk drive has a laser diode for generating laser of multiple power levels and a detecting unit for detecting laser powers to generate power feedback signals correspondingly. In the power control system, a first power control unit is used to control the read or write power of the laser. The first power control unit generates an original first power control signal to control the laser diode to emit laser with a predeteremined power level. The first power control unit receives a first power feedback signal from the defecting unit. The first power feedback signal corresponds to the power level of the laser generated corresponding to the original first power control signal. The first power control unit generates a modified first power control signal according to the original power feedback signal and a desired power level to control the laser diode to emit laser corresponding to the modified first power control signal. A second power control unit is used to control over drive power and/or a multipulse write power for the laser diode. The second power control unit receives the original and modified first power control signals from the first power control unit, and generates a modified second power control signal according to a predetermined ratio, the modified and original first power control signals, and an original second power control signal to control the laser diode to emit laser with a desired power level. 
         [0015]    The present invention also provides a method for maintaining the output power of a laser diode of an optical disk drive to improve the recording performance of the optical disk drive. In addition to the laser diode, the optical disk drive has a detecting unit for detecting laser powers of the laser diode to generate power feedback signals correspondingly. The power control method comprises generating an original first power control signal to control the laser diode to emit laser; generating a first power feedback signal corresponding to the laser generated corresponding to the original first power control signal; generating a modified first power control signal according to the first power feedback signal and a desired power level to control the laser diode to emit laser corresponding to the modified first power control signal; and generating a modified second power control signal according to a predetermined ratio, the modified and original first power control signals, and an original second power control signal to control the laser diode to emit laser with a desired power level. 
         [0016]    The advantages of the present invention include: (a) generating a compensating DAC signal to adjust the output power of the laser emitting of an optical disk drive, especially to adjust a write power of the laser emitting, for maintaining the write power in a constant state; (b) providing a high recording performance of the optical disk drive with a reduced cost by compensating the power variation due to the temperature variation without a high-speed APC circuit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  shows a diagram of two characteristic relationship lines of the reading DAC value relative to different read powers at two specific temperatures. 
           [0018]      FIG. 2  illustrates a schematic diagram of a simplified structure of the optical disk drive in accordance with the present invention. 
           [0019]      FIG. 3  illustrates a detailed embodiment of the present invention for exemplifying a method of getting a modified DACr value from the read power signal VRDCO and read power values. 
           [0020]      FIG. 4  illustrates another detailed embodiment of the present invention for exemplifying a method of getting a modified DACw value from the write power signal VWDC 1 O and write power values. 
           [0021]      FIG. 5  illustrates a further detailed embodiment of the present invention for exemplifying a method of getting a modified DACod value from the write power signal VWDC 2 O and write power values. 
           [0022]      FIG. 6  illustrates a detailed embodiment of the present invention for exemplifying a method of calculating a new DACod value from the read power signal VRDCO and read power values. 
           [0023]      FIG. 7  illustrates another detailed embodiment of the present invention for exemplifying a method of calculating a new DACod value from the write power signal VWDC 1 O and write power values. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]    By equation (6), we can introduce a characteristic index δ under different temperatures to calculate a compensating power ΔPwc for adjusting a write power of a writing channel of the APC circuit, shown as equation (7). 
         [0000]      Δ Pwc=δ×ΔPr   (7) 
         [0025]    Consequently, a compensating DAC value wDACc can be derived by introducing the equation (4) for compensating the output power of the laser emitting unit, shown as equation (8). 
         [0000]    
       
         
           
             
               
                 
                   wDACc 
                   = 
                   
                     
                       
                         Δ 
                          
                         
                             
                         
                          
                         wDAC 
                       
                       
                         Δ 
                          
                         
                             
                         
                          
                         wP 
                       
                     
                     × 
                     Δ 
                      
                     
                         
                     
                      
                     Pwc 
                   
                 
               
               
                 
                   ( 
                   8 
                   ) 
                 
               
             
           
         
       
     
         [0026]    Finally, we can obtain the compensating DAC value by realizing the above-mentioned equations to generate a compensating power for maintaining the output power of the laser emitting unit in a constant level. 
         [0027]      FIG. 2  shows a schematic diagram of a simplified structure of the optical disk drive in accordance with the present invention for generating an optimized laser power. The optical disk drive comprises a pickup-head comprising a photo detecting unit  10  and a laser emitting unit (e.g. a laser diode)  12 , a sample and hold circuit  14  for read power signals, a sample and hold circuit  16  for write power signals, a read power control unit  18 , a write power control unit  20 , an analog-to-digital converter (ADC)  25 , an advance power control unit  30 , a digital-to-analog converter (DAC)  40 , and a laser driver  50  for driving the laser emitting unit  12 . 
         [0028]    The photo detecting unit  10  detects current laser power of the laser diode and transmits the power feedback signals to the sample and hold circuits  14 ,  16 . The sample and hold circuits  14 ,  16  sample the current read power feedback signal and current writing feedback power signal then transmit a sampled read power feedback signal and a sampled write power feedback signal to the read and write power control units  18 ,  20 , respectively. The read and write power control units  18  and  20 , each of which can be referred to as “a first power control unit”, generate and output a power control signal (VRDCO or VWDC 1 O as shown in  FIG. 2 ) according to comparing the power feedback signals and a predetermined DAC value. 
         [0029]    The power control signals VRDCO and VWDC 1 O are voltage values, which are converted into digital signals by the ADC  25  and transmitted to the OD/MP power control unit  30 . The advance power control unit  30 , which can also be referred to as a second power control unit, receives original and modified read or write power control signals (also referred to as first power control signals) from the ADC  25  and generates a modified (second) power control signal according to a predetermined relationship among the read or write power control signals and an original second power control signal so as to control the over drive power or multipulse write power of the laser diode. 
         [0030]    The laser drive  50  receives the modified second power control signal, VWDC 2 O, which indicates a modified control value, to control the laser power. The laser driver  50  drives the laser emitting unit  12  by a proper power in accordance with the read power control signal VRDCO, write power control signal VWDC 1 O and OD/MP power control signal VWDC 2 O. 
         [0031]      FIG. 3  illustrates a detailed embodiment of the present invention for exemplifying a method of getting a compensating DACr value from the read power control signal VRDCO and read power levels. The DACr value is used to generate the read power of the optical disk drive. The method of getting the DACr value comprises the steps of:
   Step S 800  Start;   Step S 802  The read power control unit  18  sets a read channel DAC value DACr 1 ;   Step S 804  The photo detecting unit gets a first read power Pr 1 ;   Step S 806  The read power control unit  18  generates a first VRDCO value VRDCO 1 ;   Step S 808  The laser emitting unit outputs a second read channel DAC value DACr 2 ;   Step S 810  The photo detecting unit gets a second read power Pr 2 ;   Step S 812  The analog to digital converter gets a second VRDCO value VRDCO 2 ;   Step S 814  Calculating a new VRDCO value VRDCO_md from the VRDCO transfer function by using VRDCO 1 , VRDCO 2 , Pr 1  and Pr 2  values;   Step S 816  Calculating a new DACr value DACr_md from the DACr transfer function by using DACr 1 , DACr 2 , Pr 1  and Pr 2  values;   Step S 818  Saving the new DACr value DACr_md and new VRDCO value VRDCO_md in a memory;   Step S 820  End.     
         [0043]      FIG. 4  illustrates another detailed embodiment of the present invention for exemplifying a method of getting a modified DACw value from the write power signal VWDC 1 O and write power values. The DACw value is used to adjust the write power of the optical disk drive. The method of getting the DACw value comprises the steps of:
   Step S 900  Start;   Step S 902  The laser emitting unit outputs a first write channel DAC value DACw 1 ;   Step S 904  The photo detecting unit gets a first write power Pw 1 ;   Step S 906  The analog to digital converter gets a first VWDC 1 O value VWDC 1 O 1 ;   Step S 908  The laser emitting unit outputs a second write channel DAC value DACw 2 ;   Step S 910  The photo detecting unit gets a second write power Pw 2 ;   Step S 912  The analog to digital converter gets a second VWDC 1 O value VWDC 1 O 2 ;   Step S 914  Calculating a new VWDC 1 O value VWDC 1 O_md from the VWDC 1 O transfer function by using VWDC 1 O 1 , VWDC 1 O 2 , Pw 1  and Pw 2  values;   Step S 916  Calculating a new DACw value DACw_md from the DACw transfer function by using DACw 1 , DACw 2 , Pw 1  and Pw 2  values;   Step S 918  Saving the new DACw value DACw_md and new VWDC 1 O value VWDC 1 O_md in a memory;   Step S 920  End.     
         [0055]      FIG. 5  illustrates a further detailed embodiment of the present invention for exemplifying a method of getting a modified DACod value from the write power signal VWDC 2 O and write power values. The DACod value is used to adjust the over-drive write power of the optical disk drive. The method of getting the DACod value comprises the steps of:
   Step S 1000  Start;   Step S 1002  The laser emitting unit outputs a first write channel DACod value DACod 1 ;   Step S 1004  The photo detecting unit gets a first write power Pod 1 ;   Step S 1006  The analog to digital converter gets a first VWDC 2 O value VWDC 2 O 1 ;   Step S 1008  The laser emitting unit outputs a second write channel DACod value DACod 2 ;   Step S 1010  The photo detecting unit gets a second write power Pod 2 ;   Step S 1012  The analog to digital converter gets a second VWDC 2 O value VWDC 2 O 2 ;   Step S 1014  Calculating a new VWDC 2 O value VWDC 2 O_md from the VWDC 2 O transfer function by using VWDC 2 O 1 , VWDC 2 O 2 , Pod 1  and Pod 2  values;   Step S 1016  Calculating a new DACod value DACod_md from the DACod transfer function by using DACod 1 , DACod 2 , Pod 1  and Pod 2  values;   Step S 1018  Saving the new DACod value DACod_md and new VWDC 2 O value VWDC 2 O_md in a memory;   Step S 1020  End.     
         [0067]      FIG. 6  illustrates a detailed embodiment of the present invention for exemplifying a method of calculating a new DACod value from the read power signal VRDCO and read power values. The method of calculating the new DACod value comprises the steps of:
   Step S 1100  Start;   Step S 1102  Determining whether the recording procedure is finished, if the recording procedure is finished, go to step S 1114 , otherwise go to step S 1104 ;   Step S 1104  Getting a current command value of output read power Pro;   Step S 1106  Calculating an orginal VRDCO value VRDCO_ori from read power to VRDCO transfer curve by Pro value;   Step S 1108  The analog to digital converter gets a modified VRDCO value VRDCO_md;   Step S 1110  Calculating a new DACod value DACod_md from read power to DAC transfer curve by VRDCO_ori and VRDCO_md values. The relationship of read power to DAC transfer curve is shown as equation (9):     
         [0000]    
       
         
           
             
               
                 
                   DACod_md 
                   = 
                   
                     
                       Ratio 
                       × 
                       
                         ( 
                         
                           VRDCO_md 
                           - 
                           VRDCO_ori 
                         
                         ) 
                       
                       × 
                       
                         
                           Δ 
                            
                           
                               
                           
                            
                           P 
                         
                         
                           Δ 
                            
                           
                               
                           
                            
                           V 
                         
                       
                       × 
                       
                         
                           Δ 
                            
                           
                               
                           
                            
                           rDAC 
                         
                         
                           Δ 
                            
                           
                               
                           
                            
                           rP 
                         
                       
                     
                     + 
                     DACod_ori 
                   
                 
               
               
                 
                   ( 
                   9 
                   ) 
                 
               
             
           
         
       
       
         Step S 1112  Outputting the new DACod value DACod_md, and back to step S 1102 ; 
         Step S 114  End. 
       
     
         [0076]      FIG. 7  illustrates another detailed embodiment of the present invention for exemplifying a method of calculating a new DACod value from the write power signal VWDC 1 O and write power values. The method of calculating the new DACod value comprises the steps of:
   Step S 1200  Start;   Step S 1202  Determining whether the recording procedure is finished, if the recording procedure is finished, go to step S 1214 , otherwise go to step S 1204 ;   Step S 1204  Getting a current command value of output write power Pwo;   Step S 1206  Calculating an original VWDC 1 O value VWDC 1 O_ori from write power to VWDC 1 O transfer curve by Pwo value;   Step S 1208  The analog to digital converter gets a modified VWDC 1 O value VWDC 1 O_md;   Step S 1210  Calculating a new DACod value DACod_md from write power to DAC transfer curve by VWDC 1 O_normal and VWDC 1 O_real values. The relationship of write power to DAC transfer curve is shown as equation (10):     
         [0000]    
       
         
           
             
               
                 
                   DACod_md 
                   = 
                   
                     
                       Ratio 
                       × 
                       
                         ( 
                         
                           VWDC1O_md 
                           - 
                           VWDC1O_ori 
                         
                         ) 
                       
                       × 
                       
                         
                           Δ 
                            
                           
                               
                           
                            
                           P 
                         
                         
                           Δ 
                            
                           
                               
                           
                            
                           V 
                         
                       
                       × 
                       
                         
                           Δ 
                            
                           
                               
                           
                            
                           wDAC 
                         
                         
                           Δ 
                            
                           
                               
                           
                            
                           wP 
                         
                       
                     
                     + 
                     DACod_ori 
                   
                 
               
               
                 
                   ( 
                   10 
                   ) 
                 
               
             
           
         
       
       
         Step S 1212  Outputting the new DACod value DACod_md, and back to step S 1202 ; 
         Step S 1214  End. 
       
     
         [0085]    It is noted that equation (9) or (10) is set to approach the required DAC curve. The power signals can be read or write power signals. The term ΔDAC/ΔP can utilize the read power related value (equation (1)) or the write power related value (equation (3)). Furthermore, the terms ΔP/ΔV and ΔDAC/ΔP may even incorporated into the term “Ratio” in some circumstances. 
         [0086]    By utilizing the method of the present invention, an optimized write power of the laser emitting unit of the optical disk drive can be determined by introducing the current reading or write power signals of the laser emitting unit with a predetermined relationship of the output power of the laser emitting unit relative to the DAC value. 
         [0087]    The advantages of the present invention include: (a) generating a modified DAC signal to adjust the output power of the laser emitting of an optical disk drive, especially to adjust a write power of the laser emitting, so that the write power is maintained in a constant level; (b) providing a high recording performance of the optical disk drive with a reduced cost by compensating the power variation due to the temperature variation without a high-speed APC circuit. 
         [0088]    As is understood by a person skilled in the art, the foregoing preferred embodiments of the present invention are illustrative rather than limiting of the present invention. It is intended that they cover various modifications and similar arrangements be included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structure.