fig4 a - 4d illustrate an exemplary method of operation of a dmd in accordance with the invention . in this example , a memory cell having three sub - cells 54 , 55 , 56 is associated with each mirror cell dm mn , as is illustrated in fig2 for storing three - bit data codes . in practice , the number of bits in each code , and correspondingly the number of memory sub - cells , preferably will be greater , e . g . seven . fig4 a and 4c illustrate the production by different sources of a succession of three - bit binary display codes d1 mn , d2 mn , d3 mn , at respective frame rates , for the activation of mirror cell dm mn in three successive frames . in this example , the frame rate in fig4 a is 72 hz ( e . g . from a computer ) while the frame rate in fig4 c is 60 hz ( e . g . from a television broadcast source ). the frame periods corresponding to these frame rates have the respective durations t a = 1 / 72 second ( 13 . 9 ms ) and t c = 1 / 60 second ( 16 . 7 ms ), respectively . the dmd successively stores these codes , from either of the sources , in a portion of the register 18 associated with the column line c n . the codes are stored in the register at whichever frame rate they are received . simultaneously , codes for activation of each of the other mirror cells in the array are successively stored in a respective portion of the register 18 associated with the column line for that cell . fig4 b and 4d illustrate how the codes d1 mn , d2 mn , d3 mn , for activating mirror cell dm mn are processed after they are stored in the register 18 . that is , the dmd activates the mirror cell for each code at a subframe rate of 360 hz , which is the lowest integral multiple of the 60 and 72 hz frame rates . thus , each subframe has a period t s of duration 1 / 360 second ( 2 . 8 ms ). note that , while in this simple example only two different source frame rates are considered , the dmd could be readily adapted to receive data at significantly more than two different rates by utilizing a different subframe rate which is an integral multiple of all of the frame rates . for example , if display codes from a third source are also to be received at a frame rate of 24 hz ( commonly used in motion - picture films ), the same subframe rate of 360 hz could be used . note that fig4 b and 4d show the entire 2 . 8 ms duration of each subframe period t s as being utilized to activate the associated mirror cell dm mn , i . e . to read the three bit codes which are successively stored in the respective memory cell 54 , 55 , 56 . in practice , time must also be allotted to write each of the codes d1 mn , d2 mn , d3 mn , . . . into the memory cell . a first approach is to both write and read the respective code during each subframe period t s . this , however , requires a high write speed , because the time allotted to write each code in the memory cell would ideally occupy only a small portion of each subframe relative to the portion utilized for reading ( i . e . activating the associated mirror ). a second approach is to utilize one of the subframe periods t s to write the code into the memory cell and to utilize the remaining subframe periods t s to repeatedly activate the mirror cell . in either approach , the mirror cell is activated at the rate 1 / t s . fig5 illustrates how the second approach can be utilized to activate each mirror cell in accordance with a modified form of a data code stored in its associated memory cell , i . e . in a distributed duty cycle sequence which makes use of the invention claimed in u . s . patent application ser . no . 08 / 495 , 290 ( pha 21992 ). in this example , it is presumed that a 72 hz source is providing seven - bit binary display codes b 6 b 5 b 4 b 3 b 2 b 1 b 0 to the dmd during each period of duration t a , and that the code b 6 b 5 b 4 b 3 b 2 b 1 b 0 = 1001101 has been stored in a portion of the register 18 associated with the column line c n . as in the example of fig4 b , five subframes of duration t s are available for storing the code in the memory cell and activating the associated mirror cell dm mn . during the first of these subframes , i . e . subframe 1 , the code is stored in the memory cell . in each of the next four of these subframes , i . e . subframes 2 through 5 , the digital light modulating mirror is modulated with a modified form of the code . that is : during subframe 2 , the mirror is modulated in accordance with the states of the bits b 6 b 5 b 4 b 3 b 2 b 1 for the relative durations illustrated . during subframe 3 , the mirror is modulated in accordance with the states of the bits b 6 b 5 b 4 b 3 b 2 b 0 for the relative durations illustrated . during subframe 4 , the mirror is modulated in accordance with the states of the bits b 6 b 5 b 4 b 3 b 2 b 1 for the relative durations illustrated . during subframe 5 , the mirror is modulated in accordance with the states of the bits b 6 b 5 b 4 b 3 b 2 for the relative durations illustrated . fig6 illustrates another approach for activating each mirror cell in accordance with a modified form of a data code . in this approach , a data code is both written into and read from the respective memory cell during each subframe , but the code is modified in each of subframes 2 through 5 . this approach is particularly useful for performing filtering functions such as temporal filtering where interpolated codes are produced by combining data codes from different frame periods . in the example of fig6 a code d1 mn , received at the 72 hz rate represented by fig4 a , is written / read identically or in interpolated form ( combining d1 mn and d2 m ) during each of five subframe periods of duration t s , as follows : during subframe 1 , the code d1 mn is written ( stored ) in the memory cell and then read by activating the associated mirror cell in accordance with the states of the bits of the code d1 mn for durations corresponding to the respective weights of the bits . during subframe 2 the code d1 &# 39 ; mn ( having the interpolated value 4 / 5 d1 mn + 1 / 5 d2 m ) is written in the memory cell and then read by activating the associated mirror cell in accordance with the states of the bits of the code d1 &# 39 ; mn for durations corresponding to the respective weights of the bits . during subframe 3 , the code d1 &# 34 ; mn ( having the interpolated value 3 / 5 d1 mn + 2 / 5 d2 mn ) is written in the memory cell and then read by activating the associated mirror cell in accordance with the states of the bits of the code d1 &# 34 ; mn for durations corresponding to the respective weights of the bits . during subframe 4 the code d1 &# 39 ;&# 34 ; mn ( having the interpolated value 2 / 5 d1 mn + 3 / 5 d2 mn ) is written in the memory cell and then read by activating the associated mirror cell in accordance with the states of the bits of the code d1 &# 39 ;&# 34 ; mn for durations corresponding to the respective weights of the bits . during subframe 5 , the code d1 &# 34 ;&# 34 ; mn ( having the value 1 / 5 d1 mn + 4 / 5 d2 mn ) is written in the memory cell and then read by activating the associated mirror cell in accordance with the states of the bits of the code d1 mn for durations corresponding to the respective weights of the bits . fig7 a illustrates one embodiment of an arrangement for producing such interpolated codes . the arrangement includes a data compressor 10 for dividing each received frame period into a plurality of subframes and an interpolator 12 for inserting interpolated codes into some of the subframes . in the specific example shown , the data compressor receives data codes d1 , d2 , d3 , . . . at an input clock rate ck in ( e . g . 72 hz ), divides each frame period into five subframes by producing output data subframes at an output clock rate ck out = 5 ck in , and inserts the received data codes into the first of each five subframes , while leaving the remaining four subframes free for interpolated codes . in fig7 a the data compressor inserts all zeroes in the remaining subframes , but the values of these codes may be any value , because they will be replaced in the interpolator by the codes d1 &# 39 ;, d1 &# 34 ;, d1 &# 39 ;&# 34 ;, d1 &# 34 ;&# 34 ;. fig7 b illustrates an exemplary embodiment of the interpolator 12 . in this embodiment , the interpolator includes frame stores a and b for sequentially storing the data codes d1 , d2 , d3 , . . . inserted by the data compressor 10 into each of the first subframes , digital multipliers 121 , 123 , and a digital summer 125 . multiplier 121 has a first input for receiving data stored in frame store a and a second input for receiving a time - varying digital coefficient signal c a . similarly , multiplier 123 has a first input for receiving data stored in frame store b and a second input for receiving a time - varying digital coefficient signal c b . digital summer 125 has first and second inputs , for receiving products produced by the multipliers , and produces sums of these products at its output . fig7 c is a timing diagram demonstrating how the interpolator of fig7 b may be operated while receiving data from the data compressor 10 of fig7 a . during every subframe a read a / b pulse is applied to both frame stores to effect appearance at their respective outputs of whatever data is contained in these stores . during initialization , however , i . e . during the first four subframes of frame 1 in , when no data has yet been stored in frame store b , the time - varying coefficients c a and c b have continuous zero values to effect production of a continuous zero - value code at the output of the summer 125 . initialization includes application of a write a pulse to frame store a , during the first subframe of frame 1 in , when the code d1 is applied to the input of the interpolator , to effect storage of this code . during the fifth subframe of frame 1 in ( corresponding to the first subframe of frame 1 out produced by the interpolator ), a write b pulse is applied to frame store b to effect copying of the code d1 into store b , such that the code d1 is now stored in both frame stores . also during this subframe , the coefficients c a and c b have the values 0 and 1 , respectively . the read a / b pulse occurring during this subframe causes the code d1 to be applied by the frame stores to both multipliers , resulting in production by the summer of the output ( 0 ) d1 +( 1 ) d1 = d1 . during the first subframe of frame 2 in ( corresponding to the second subframe of frame 1 out ), a write a pulse is produced while the code d2 is applied to the input of the interpolator to effect storage of this code in frame store a . the read a / b pulse occurring during this subframe causes the code d2 stored in frame store a and the code d1 stored in frame store b to be applied to the first inputs of multipliers 121 and 123 , respectively . also during this subframe , the coefficients c a and c b have the values 1 / 5 and 4 / 5 , respectively , such that the summer produces the code d1 &# 39 ;= 1 / 5 d2 + 4 / 5 d1 . during the second through fourth subframes of frame 2 in ( corresponding to the third through fifth subframes of frame 1 out ), the coefficients change as illustrated in fig7 c to successively effect production at the summer output of the codes d1 &# 34 ;= 2 / 5 d2 + 3 / 5 d1 , d1 &# 39 ;&# 34 ;= 3 / 5 d2 + 2 / 5 d1 , and d1 &# 34 ;&# 34 ;= 4 / 5 d2 + 1 / 5 d1 . during the fifth subframe of frame 2 in ( corresponding to the first subframe of frame 2 out ) the interpolation process repeats the above - described steps , but now for production of the codes d2 , d2 &# 39 ;, d2 &# 39 ;, &# 39 ; d &# 39 ;&# 34 ;, d2 &# 34 ;&# 34 ;, d3 . . .