Patent GB-1404672-A (GB)
Title: Apparatus for the reproduction of pictorial images
Inventor: KELLER HANS DR
IPC: H04N1/62
Filed: 1972-07-27
Abstract: 1404672 Copying by scanning DR ING RUDOLF HELL GmbH 27 July 1972 [28 July 1971] 35259/72 Heading H4F In a point by point, line by line colour picture reproduction system a sequence of picture signals for reproduction is formed by sequentially selecting portions from a plurality of digital picture signals. The picture signals are produced by opto-electrical scanning and the selection is performed in accordance with masking signals produced by opto-electrically scanning a mask. Overall system.-Digital picture signals are redorded on separate magnetic tapes with timing information stored in a further track. A further tape carries picture point data for the mask and may comprise superimposed data for several different masks. Outputs from the various tapes are supplied through respective intermediate stores to processing circuitry under the control of a timing device. In addition constant signal values derived from potentiometers through analoguedigital converters may be supplied to the processing circuitry. Knockout masking (Fig. 2).-Data bits (six per picture point) from two picture signal tapes and two constant signal generators are supplied on lines 15/1 to 15/6, 16/1 to 16/6, 17/1 to 17/6 and 18/1 to 18/6 to temporary storage transfer registers 22, and mask data bits (two per picture point) are supplied on lines 13/1 and 13/2 to further transfer registers 22, all the registers operating under the control of timing signals on line 11. The positive and negative outputs from registers 22 in the masking signal channel are connected to NAND gates 23 to produce a signal on a different line 25 to 28 for each possible combination of inputs 13/1, 13/2. One AND- gate of each of the AND/OR gate combinations 24/1 to 24/6 is thereby enabled and the data bits of one of the signals 15, 16, 17, 18 are supplied to lines 19/1 to 19/6. Shading alteration (Fig. 3, not shown).-The data bits of one of the picture signals may be subjected to tonal variation by supplying the outputs of transfer registers (22) to a decoding circuit comprising 64 six-way AND-gates. The decoded output causes the read-out of a unique picture signal from a permanent core store, the resulting six-bit picture signal being supplied to AND-gates which are simultaneously enabled by a masking signal on one of the lines 25 to 28 (as in Fig. 2). Picture point value averaging (Fig. 4). -This technique may be used to soften the picture in certain areas while retaining the sharpeness in others. Five neighbouring picture point signals are stored in shift register 34, with picture values 6, 4, 5, 2 and 1. These values are added in pairs in cascade to produce a total (61) which is divided by 16 in divider 36 to give a weighted mean value. Either the output of divider 36 or the middle picture point value (5) is then gated to the output using the masking signal on line 13. In a modification the last value fed in is used as the alternative output instead of the middle picture point value and an extrapolation technique is used to derive the weighted mean for the last of the stored picture points (Fig. 5, not shown). These arrangements may be used to reproduce a picture in which details of a landscape are retained but skin tones are rendered more softly. Diffusion masking (Fig. 6).-Averaging may be performed over picture points adjacent the picture point concerned in the preceding and following line, as well as in the same line. Thus, intermediate stores 45, 46, 47 store three successive lines and switches 48, 49, 50 ensure that the line which is central in time appears at 52, the preceding line at 51 and the following line at 53. Three adjacent picture point values in each line are stored in shift registers 54. The middle picture point value is supplied to multipler 57 where it is multiplied by eight. The other eight values are added at 56 and the difference derived at 60 between this sum and the output of muliplier 57 is gated by the masking signal through multiplier 63 to adder 64. This signal is added to the output from multiplier 57 to provide a modified picture point signal. Black letter masking.-In order to avoid a white or coloured edge at one side of a black letter produced by a mask, due to misregistration between the letter inserted during the black printing and the corresponding space produced by the colour printers the boundaries of the letter are displaced towards the centre of the letter in the colour printers and the colour signals preceding the letter are continued during the time the letter masking signal lasts. The first effect is obtained using the system shown in Fig. 7 in which the mask signal is stored in tape store 42, components 44 to 55 operating as in Fig. 6. The middle value from store 55 is supplied to decoder 68 which generates a signal on line 69/1 for the presence of the letter signal in 55 and a signal on line 69/2 for the presence in 55 of a signal for a portion of the mask surrounding the letter signal. The mask signals for points surrounding that corresponding to 55 are supplied to decoder 56 which decodes for the presence of a letter signal in each storage cell and supplies outputs to eight-way AND gate 70 whose inverted output is fed to AND-gate 75. The latter gate thus produces an output when there is an output on line 69/1 or 69/2 and the letter signal is not present in all the storage cells of the shift registers. During this period the picture signals from tape store 66 are passed to the output. As soon as the letter signal completely enters the shift registers the picture signals are blocked. The picture and masking signals for storage are produced by scanning the picture or mask (92, Fig. 8, not shown) mounted on a rotating drum, synchronization signals being produced by an auxiliary photodetector viewing a scale carried by the drum and by a stationery inductive pulse emitter (103).